CO2 issues? Read this

[Tom Barr]

CO2 is one of those critical things that aquatic plants folks should really focus on.
I've nagged folks about this for a very long time, and I will likely nag you to the grave.
Complacent experts, newbies, test kit freaks, all of you(and myself included).
Poor CO2 reduces growth and is responsible for nearly 95% of all algae related issues.

Now KH test kit variance is one issue, making a reference standard to compare you KH test to is a very WISE idea to check the accuracy. I've seen many folks have very high CO2 predicted levels, yet fish were fine, but another than has barely 30ppm and the fish are gasping. It cannot be that both are at the same CO2ppm level becaused we would expect to see the same behavior from the fish. Instead we see very wide ranges and impacts on the fish(as well as plants).

So it's much more likely that it is the testing method, rather than anything else.
pH is the best thing as far as accuracy for CO2 measurements using a pH probe and no electrical equipment runnign when the pH is measured(stray current will depress the pH giving false high ppm CO2 levels).

KH test kits have consistency issues (see recent post) and in some places, although rare, non bicarbonate alkalinity exists(recent poster in NM has significant borate alkalinity, desert regions generally).

Addressing this issue by making a reference sample will take care of the KH issue.

The next issue is more interesting for many of of you.
I'd suggested that the venturi DIY reactor I have shown folks on my site is better than any reactor. Well, initially, and perhaps partially true, is the purpging effect of gas build up.
This gas is some O2 and some CO2, but very little "air".

As the gas is expelled, consistently I see better growth, this is not due to O2.
So why would a mist of tiny CO2 bubbles vs dissolved CO2 in solution do better for growing plants?

I addressed the O2 issue simply, I used a diffuser disk for CO2(no O2 gas build up occurs).
But that did not do it __alone__.

I wondered why.

So I placed the diffuser disc near similar current like that produced by the venturi reactor after is starts mistuing the gas out the bottom.

Lo and behold, Bam! Excellent similar growth.
Not the kind of so so growth, but pearling like nothing you have ever seen or perhaps only in a very few well run tanks right after a water change. But I'd not done a water change for a week.
I tried it several times on 4 tanks, same result in each tank. Day after day, intense pearling even with fair good current.

So why would this mist be better than dissolved CO2?

For one thing, it's __pure CO2 gas__, which flows much faster than dissolved CO2 liquid.
The flux rate is much faster with pure CO2 gas than CO2 dissolved in water, so the plants get more CO2 and a more concentrated form.

Some folks may not like the bubbles, some might not like pearling.
But I sure do.

I can say that the venturi effect is one of CO2 now, and not of O2 by using the diffuser disc to rule out O2.

So that just left CO2 and the gas vs dissolved form to consider why one method was better in terms of plant than another.

Both flow and actually having some gas in the tank itself seems to be the key here.
So those disc are not so bad and neither are the venturi reactors.

You can make a purge loop for external reactors by making a hole 1/2 down and running the air line back to the intake for the power head, caniter filter etc, this will not add bubbles but will reduce the gas build up inside the reactor.

The real issue is having gas bubbles in the tank and putting them where the plants are in that form.

I think folks should really consider this/these idea/s and try them.
I've had very intense pearling and have over the entire routine time frame, not just for a day or a few days.

Be careful and watch the fish, CO2 levels when doing this, I've not had any fish issues yet. Make sure there is some surface movement. If you use disc, clean them often(monthly).

For larger tanks, they make 6x1" diffuser stones for about 60$ than can be used set along the bottom back gravel layer so they will not be seen. wwww.aquaticeco.com sells them if interested.

In any event, this notion of having tiny gas bubbles floating around very dissolved CO2 might solve many folk's problems and improve those who seek better growth.

Nitrogen is an essential element, but only 1.5%, vs 40+ % for Carbon, it is very very wise to focus on this if you seek better growth.

With good CO2 levels, even the wimpy plants do very well(Tonia, ES, Eirocauleon) algae dies, pearling as intense as you have ever seen it day after day will occur.

I think the gas bubbles might also be less of an issue for fish since it's not dissolved into solution also.

The nutrients can be addressed easily by doing EI, so you know there's enough, so all that's left to really focus on is the CO2.

So I have been playing around trying to figuire out a good way to reproduce max CO2 without causing issues for fish, and adding enough for the plants.

The CO2 mist + current seems to be the best method.

This can be done with a reactor or a diffuser stone/disc.

Also, folks using spray bars, turn them vertically, next to the intake and place the disc down near this also. This hides the bar, the disc, intake all in one place. Having the spray bar current blowing along the back side the tank wall seems to give good flow characteristics+ near the disc, the water blows out and away from the intake and circles around to the intake.
Since water is being blown directly away from the intake, this gives optimum mixing.
Since water is being blown directly on top of the difusser, all the bubble mist is being blown all over the tank.

The results are easy to see.

The other issue is not to trust the test kits so much until you see the type of pearling like this, no BBA growth etc, slowly and patiently add more CO2 till you get the pearling and good growth. Basically use the test to get close, then tweak(add more) carefully and slowly.
Do not go overboard, do it slowly and observe the plants/fish. Your test may give you high numbers, but if the fish are fine, then it's okay.
Turing off CO2 at night will help add the margin of safety also. We add CO2 for the plants, not to maintain pH. Some leave it 24/7, but mainly out of convenience rather than methodology. With disc, running them at night can cause issues, anyway, you can save 2-3x the gas by not running it at night. We know fish don't care about the pH change.


Regards,
Tom Barr

www.BarrReport.com

[rrguymon]

Yikes, I just made this. http://www.hoftiezer.net/personal/aquaria/ Some glue is curing as I wright this. I wanted to get this http://www.aquariumplants.com/cgi-bin/cart/pr009.html outta the tank. Maybe I will rethink this a bit.

Rick

[CrownMan]

Hi Tom,

On another board, you helped me with a non-CO2 30Long, High Light system and you were right. I floundered and last Friday, hooked up an old Aqua Medic CO2 reg, bubble counter, new PH Monitor and full tank but I didn't have a diffusser. I looked around and had an old Duetto DJ-50 inside filter that has an aerator built in on the top of the filter. I installed the CO2 hose into this, new sponges and instant CO2 diffuser that is putting out a fine mist of CO2 bubbles which then get caught in the current from my Power Head on the UG (not a RFUG unfortunately). My CO2 is at 30ppm and plants are growing like crazy. I can't tell, though, if the plants are perling or if the fine mist of bubbles is just collecting on them and then rising. Seems to work well though.

Thanks for the Help

Mike

[fishface]

I can't tell, though, if the plants are perling or if the fine mist of bubbles is just collecting on them and then rising. Mikevery good point here...how do you know??

[rrguymon]

I have been looking at the venturi you have on your DIY page. I think I can use the external reactor I made, to put on the output of my canister, in the same fashion.

I will drill the two small holes 2" and 2.5" down on the external reactor tube. I will route the hose from the one 2" down into the venturi input to a power head in the tank and route the hose from the the one 2.5" down to spill anywhere into the tank.

I think the top outlet might give the in tank power head a similar mist of CO2 bubbles and the bottom outlet will burb or expel any excess gas.


Rick

[PeterGwee]

Tom, could it be that those bubbles "flying" out of the DIY venturi reactor are actually O2 bubbles being caught onto plant leaves and not from plant growth?

Regards
Peter Gwee

[TerryB]

Tom,

There is an interesting experiment you could try along these lines. I used to work for a company that has a membrane based gas/liquid exchange technology. Been awhile since I worked for them - but using thier modules - should be able to get max CO2 concentrations into the water. There would be no mist or bubbles - its an extremely efficient diffusion reactor. I have been trying for awhile to get them to send me one (they probably won't because I am sure they think I am working for some competitor and the aquarium story is a ruse). This is the stuff used in heart lung machines for blood oxygenation/co2 removal.

Only down sides are biofilm forming on membrane and impact on efficiency and cost. You would have to clean them after awhile possibly. Any interest? I can pursue it a little more. You would be the right guy to test since you have the "other data" as reference point and observation.

Terry

[Tom Barr]

Tom, could it be that those bubbles "flying" out of the DIY venturi reactor are actually O2 bubbles being caught onto plant leaves and not from plant growth?

Regards
Peter Gwee

Well, hehe, enter the diffuser disc, which has no such issue as a control for this same issue.

Same observation............

Try again:)

Sorry Terry, biofilms and passive reactors are not my thing.
Bioflim issue is a biggy.
Our lungs diffuse CO2 out/O2 in through liquid(our blood) the same way as reactors do. Gas is much easier to breath in and we get far more exchange than we would with water(this can be done with super sat O2 liquid and deep sea divers etc, but you can breath much better with O2 gas!)

Mike, see the control I used with the disc, so the answer is no, it's plant production.

You can also do a O2 test and see if you have higher O2 levels with or without(this is what I did as well as simply observe plant health etc).

I think this will bug folks for a long time.
It's counter to what you woud think, since saving every last bubble seems "better" and would produce better growth, but it is an issue of delivery and in what concentration(100% CO2 gas).



Regards,
Tom Barr

[PeterGwee]

Tom, how about feeding the CO2 gas into a powerhead output with a spraybar at the bottom back area of the tank? Loads of misting around in the tank and the bubbles gets to all parts of the plants pretty good. Frankly, I did get that result some time back when you suggest that method of a powerhead with spraybar but thought those were some form of gases and not real pearling.

Regards
Peter Gwee

[Cornhusker]

:) tom,the issue of a staginate 55 gal tank i asked about in recent thread has responded to turning co2 way up to increase small bubbles coming out of bottom of diy reactor. also set sraybar to get surface motion. this tank has never pearled. now there is action everywhere in tank. could this be the step in the right direction? i am finding out that co2 and more co2 is the only way for a successful tank. thank you, regards,cornhusker :) :)

[jonathan11]

Grrr, just when I think everything is going good......Must profess my ignorance, diffuser disk- not familiar with them- could someone briefly explain what they are, perhaps name of a good one, and place to get them?
Tried www.aquaticeco.com, couldn't seem to find that diffuser airstone- again, can someone help me out? Thx from the old geezer,

Walter :gw :D :D

[wob]

Tom,
I have a very large tank (150g, 72x24x24) and was wondering what diffusers were you looking at on aquaticeco.com? Also, do you just hook the co2 line directly to the diffusers that would be at the back of the tank?

I have not built a CO2 reactor yet so I'm pretty flexible with trying any of these setups.

Thanks,
Robert

[brad]

You`re a sucker for punishment Tom. :) First the po4, now co2. I will likely stick with my reactor as I can just imagine the current it would take to push those bubbles across the tank would make my plants droop that direction so......

Anyway, kudos to you Tom for continuing to look into issues most people accept as already being researched. Even if you`re gonna get, as you would say, poo-pooed for this. :rolleyes:

[Tom Barr]

Well one guy has it in for me on the APD, won't be the first time for me, probably is for him:-) He's getting the ignore as he's not contributing and playing nice nor making any sense.
He'll come around and play a more positive role later.

Alright, CO2 diffusers for large tanks:

This was in response to Terry Barber, who is a member here as well as a well known author of aquatic plants and writes for TFH on plants.

Terry sez:

>I proposed to Tom that he consider using an extremely efficient diffusion
>device that will highly saturate the water with CO2 - but no bubbles and
>make the comparison that way. This may actually tell more about whether the
>presence of bubbles actually does something more.

Already have done this and have done it with the external vs interal versions of the CO2 reactors I've made and sold to many folks here. Old stuff I have already long considered.
I've been wondering about this for a long time. Plants do not lie and I've seen the differences between both the methods with the internal CO2 venturis vs the externals.

I recently developed an external venturi, pretty cool.
Knocked Mike's 180 gal CO2 problem from hell to the good range with no other adjustments by 0.3-0.4pH units. Pearling now starts about 3 -4 hours earlier. I have not gone after it with a DO meter, but he does not care, the tank is doing much better and the algae stop growing.

I've made nearly a dozen designs over the last 12 or so years.
I have 100% of the gas in solution that is dosed for the tanks.
I've made all sorts of reactors from 1 gal to 2000 gallon tank sizes and tested them for effective usage(zero bubbles from the outflow and response times to pH drops).

I've done this method for many years, many folks have, it works well when the CO2 is near 30ppm. We did not see CO2 issues till folks started adding more light(the light was not available back then generally unless you where a DIY'er or wanted to spend the $ for MH's(I did).

My point with the gas CO2 mist, is that it definitely increased O2 levels in the tank versus the other methods. This is a standard method to measure and to quantify aquatic production(O2 evolution) in the aquatic sciences.

While pearling/growth rates are the more "practical things" many aquarist use to see and gauge their tanks, this is a bit more clear when making comparisons about whether growth is increased using say one method vs another for CO2 injection. CO2 is also a large % of uptake and resources for the plant.

The tank is still jamming along, everything look Riccia with the pearls, DO levels are sky high.
No water changes yet. You do get good CO2 levels and growth and DO, but I've gotten roughly 25% more O2 using the misty bubbles method. I need to run more repetitions though. The initial results do look good.
We'll see as time goes on.
Folks typically are unwilling to blow 300$ or more for a DO meter.
Some places make cheaper ones these days but they still ain't cheap. Test kit versions typically do not go beyond 10ppm but are relatively cheap.

>I can imagine that the bubbles are providing very high CO2 levels at the
>leaf surface where they may touch (do plants have specialized cells on their
>surface that may just suck that CO2 right up? - I don't know...need to look
>it up)....or that there is a very CO2 enriched water region around the
>outside of the bubble that they similarly enjoy.

Both.
Since the pure gas bubble is under the leaf where most plants have their stomates, the distance is minimized. All cells take in/expel O2/CO2 etc in aquaeous form (even us in our lungs).

The rate is determined by Fick's 1st law of diffusion.
http://omlc.ogi.edu/classroom/ece532/class5/ficks1.html

A distance(1), diffusivity(2) and concentrational gradient(3) are the main variables.

1. Adding CO2 mist reduces the distances(minor/not significant)
2. Gas vs a liquid. Clearly the gas can move faster (large factor)
3. Increases the concentration (probably the main factor).

These are the main mechanisms.
No one mentioned these.

The other issue, few folks have ever studied this notion of misty CO2 in nature.
For all I know, I am the first to suggest it. I have never seen anything about it in the research(gas mist vs dissolved CO2 etc).

This mist adds lots of rapid contact(even if pulsed) for the plant cells(they can store a little bit of reserve fixed CO2 and it also diffuses in the cells internally).The same is true for other nutrients. Stomates are the generalized name for the openings and guard cells are the cell types that take up CO2 and expel O2. Some aquatic plants lack stomata and guard cells, eg Hydrilla. Only one plant species (terrestrial) has none, and many of the plants we keep are amphibous(and have them).They are generally on the abaxial side of the leaf, (the underside) but Water lilies have them on the top and a few other plants have exceptions.

The CO2 in these plants diffuses directly into the cells, they do not need to transport CO2 further since the leaves are 2 cells thick. Water lilies have floating leaves and would not do well to have them on the lower side and they do not need to worry about water loss unlike terrestrial or amphibous weeds.

>but come up with another
>test that can tease out what may be going on here. Certainly it's not a
>character issue.
>What do you think?
>Terry Barber

Well, there are reactors that dissolves 100%, they are available and have been for a long time(now they are much more reasonably priced). The diffusers have been as well, and the venturi design I've sold years ago and used for nearly 12 years has been around.

The main gripe was the thing was in the tank.... even though it's more user friendly and preforms better in terms of O2 levels. I have no issue addressing the method of O2 as way to measure growth in Submersed aquatic plants or algae.

Explaining why this occured was more elusive even though it seem like it was wasting gas was less obvious.

Re-examining the concentration/gas phase transfer and direct absorption into the plant rather than the water first, was the answer.
Seems weird initially.

But so did adding PO4 way back when.
Plants don't lie though.

FYI, for folks interested in trying this at a larger scale:
http://www.aquaticeco.com/index.cfm/fuseaction/product.detail/iid/9775/cid/2339

These are relatively cheap and placed on the bottom of the tank's gravel (where they belong out of sight!), by placing a spray bar down low along the back wall of the tank and placing this in the way, the micro bubbles will go all over the plants. The only thing you see is the CO2 line going into the tank.

So simply attach the CO2 line to the spray bar to hide it.
If you use a sump, use the overflow box to hide the line.

The problem with filters, powerheads etc,(they burp and blech out large bubbles as well as smaller ones) is they do not produce the fine bubbles that a good diffuser will so you have less dispersal and contact time. Smaller bubbles means that you can more evenly distribute the bubbles and they are less affected by buoyancy.

If they dissolve, you add more, but be careful, make sure the fish are okay. I have not killed a fish to date using CO2. I have killed shrimp:) But they taste so good.

1.
The real issue though is getting your current right.
Most folks could use some improvement there.
Hide the ugly stuff, make the flow pattern better through the plants etc.
This will be the biggest user issue doing this.

2.
The other user issue, the distance the CO2 travels up before it hits the current.
I placed the disc and the venturi right at the current input so that it is immediately blasting the pure CO2 all over.

3. When paying around with CO2, be careful, it can kill fish and shrimps. If you monkey with it, make sure you are around during the time you adjust it. Do not wonder off, do not go to work after setting it in the morning. Wait till you have some time. Then watch. Be competent.
Refer back to the mechanisms also in Fick's 1st law.

Smaller tanks will have little trouble.
Larger ones might consider the large flat stones above and better flow routines.

Regards,
Tom Barr

[Cornhusker]

:) tom, when i first started using co2 i tryed the defuser made by eheim. clogged very easily,but had very fine bubbles when working properly.i noticed that the stone you recomend requires at least 25 psi to work properly. i have a factory preset eheim regulator on my 75 gal tank ,do you or anyone know how much psi this regulator is set at?regards,cornhusker :) :)

[euripides6996]

Hey Tom et al.

Some questions:
- I'm assuming that the target concentration of CO2 remains around 30ppm whether you're misting or dissolving? ('misting' sounds like the SAM equivalent of 'huffing' or 'dusting'...)

- Do the CO2 bubbles in misting contribute to the ppm?

- Does it matter what kind of diffuser is used? There are the 'standard' cintered glass diffusers which come with some CO2 kits that would seem to achieve the same objective that you mention but have relatively low surface area.

- Anyone know how you clean the diffusers? I have one with algea on it and I've no clue how to get it clean....

- When you're using both a venturi reactor and a diffuser, are you using a manifold on the tank to split the CO2 supply, a standard airline gang-valve or something else entirely? I couldn't tell from the discussion whether the airline loop in the venturi was disconnected and the 'burb' hole was connected to a diffuser...

- Does the misting only work if the leaves are large enough to 'catch' the bubble on their underside?

Thanks...

Will

[bonklers]

Tom, do you have any experience using the diffusers in your link (from Aquatic eco-systems)? I wonder how many bubbles/min you have to set your needle valve in to get that 25 psi.

As allways, you keep surprising me with your ideas.

There are just a couple of things though, CO2 diffuses much more easily than air does in water, so will the micro bubbles last long enough to dwandle around the tank? And will the bubble last longer if you cranck up the CO2 to 30 ppm first with efficient/external reactors and then go over to CO2 mist delivery?

Is there any pictures to be found how this CO2 mists' looks like? I wonder how tiny the bubbles must be.

Greets,
Bonklers

[turbomkt]

Bonklers,
It's not the BPM that you've got to adjust but rather the regulator. That's what takes your 800 or so psi of CO2 down to 15-30psi (Everybody uses what works for them, right?). After that, you use the needle valve to adjust the flow rate.

The flow rate should be a factor of supplied psi and backpressure from your method of CO2 diffusion.

--Mike

[fishface]

here's my experience after trying this method after only 2 days. i've got more thread and green spot algae than ever. but lots of bubbles... :confused: and thats the only thing in my regime i've changed.

[defdac]

Today is my first day with a wood-diffusor placed under a vertical spray-bar. A second powerhead is also making a strong current right under the surface, so the microbubbles travels to the other side of the aquarium withough reaching the surface and attaching under leaves.

Does this look ok, or have I totally misunderstood the whole thing?
http://www.defblog.se/pictures/picture1605.jpg

[unirdna]

Tom, this is my verbatim post from another thread. It was dying, and I didn't know if you would see it, so I'll post it here as well. After re-reading my post, I realize that I may come off as a bit confrontational. Note that I always try to argue the argument, not the arguer ;).

Thanks for your attention.

---------------------------------------------------------------


Interesting experiment. I'm always in favor of challenging the dogma. But, there is a huge snag in my understanding of how this works. Specifically relating to my understanding of how CO2 dissolves in water.

My own experiment: Aim my spray bar downward and bubble CO2 through the airline to the bottom of my aquarium 20 inches high. The bubble of CO2 dramatically reduces size and speed (rising to the top, against the current of the spraybar) in less than one second (it is eventually blown out of the current and slowly rises to the top of the tank). The diameter of the bubble seems to reduce in size from 4mm to approximately 1mm. Using the volume equation for a sphere (V = 4/3 • p • r³), one can quickly calculate that this would be a 94% reduction in volume (15/16). This doesn't even take water pressure into consideration - which, of course, would make the percentage even higher.

If you are unable to perform this experiment, or question the conditions in which mine was performed, try this... If you are running an inline reactor, open your needle valve wide open on the CO2, allowing your reactor to fill up to 1/4 or so CO2. Then, see how fast that stuff dissolves into solution. Seconds! And what's left? A small quantity of seemingly "stubborn" CO2 bouncing around in the reactor? More likely some other gas that does not dissolve so easily. Why would 95-99% of the CO2 dissolve in seconds, and 1-5% "decide" to not dissolve?

It is this (non-CO2 gas) that I think you are fighting so hard to disperse about your tank. - whether it be via your venturi method or the diffuser/water-movement method. In short, I would surmise that the reason you are seeing this pearling would be the result of oxygen super-satruation (as O2 is likely that "hard-to-dissolve gas that is being blown around the tank).

Until a concise, scientific explanation can be offered as to why CO2 dissolves so rapidly, yet can remain as small undissolved bubbles for lengthy periods of time under turbulent conditions, the likely conclusion is that these bubbles of gas are not CO2.

Ted

[Tom Barr]

Today is my first day with a wood-diffusor placed under a vertical spray-bar. A second powerhead is also making a strong current right under the surface, so the microbubbles travels to the other side of the aquarium withough reaching the surface and attaching under leaves.

Does this look ok, or have I totally misunderstood the whole thing?
http://www.defblog.se/pictures/picture1605.jpg

You have the general idea.

I'm coming up with some better devices to perform this.
I just need to show a pic layout of how to make them etc

The diffusers are better than the air stones IME.

Regards,
Tom Barr

[Tom Barr]

Ted,


My own experiment: Aim my spray bar downward and bubble CO2 through the airline to the bottom of my aquarium 20 inches high. The bubble of CO2 dramatically reduces size and speed (rising to the top, against the current of the spraybar) in less than one second (it is eventually blown out of the current and slowly rises to the top of the tank). The diameter of the bubble seems to reduce in size from 4mm to approximately 1mm. Using the volume equation for a sphere (V = 4/3 • p • r³), one can quickly calculate that this would be a 94% reduction in volume (15/16). This doesn't even take water pressure into consideration - which, of course, would make the percentage even higher.

The dissolving rate decreases as we over saturate the water with CO2.
This is why we have gas build up in reactors (and some degassing of the O2, but disc and airstones do not have this issue!).
The first hour, the bubbles are mostly dissolved, the last few hours, they are not.

The change in ppm of CO2 in the water affects the CO2 solubility.
It becomes harder and harder to add more beyond saturation.
While I say this, I do not know "how hard" but it seems to be relevant and worth addressing.

The other issue one of surface/volume area. The surface volume area is much greater with a smaller bubble, hence faster dissolving and thus faster response to dissolving the CO2 when dosing gas CO2.

Once the CO2 ppm is high, say 20-30ppm, then the bubbbles will presist much longer(basically the reactor/disc etc are becoming more ineffecicent once you reach higher CO2 levels).

[quote]If you are unable to perform this experiment, or question the conditions in which mine was performed, try this... If you are running an inline reactor, open your needle valve wide open on the CO2, allowing your reactor to fill up to 1/4 or so CO2. Then, see how fast that stuff dissolves into solution. Seconds! And what's left? A small quantity of seemingly "stubborn" CO2 bouncing around in the reactor? More likely some other gas that does not dissolve so easily. Why would 95-99% of the CO2 dissolve in seconds, and 1-5% "decide" to not dissolve?[quote]

This idea was addressed by using the disc and then see my comments above, also, you can try adding the CO2 and ourging the gas out later in the day after a good CO2 has built up, when the water is poor in CO2 or near ambient, see how long it takes vs later in the day.

I think you'll see a marked difference.

The CO2 ppm is not static, it does change, making this a cal math issue.

[quote]It is this (non-CO2 gas) that I think you are fighting so hard to disperse about your tank. - whether it be via your venturi method or the diffuser/water-movement method. In short, I would surmise that the reason you are seeing this pearling would be the result of oxygen super-satruation (as O2 is likely that "hard-to-dissolve gas that is being blown around the tank).
[quote]

I addressed this, simply.

I used a DO meter, this measures O2 accurately.
the only way to add more than 100% ambient levels is through plant production.

Gotcha.

[quote]Until a concise, scientific explanation can be offered as to why CO2 dissolves so rapidly, yet can remain as small undissolved bubbles for lengthy periods of time under turbulent conditions, the likely conclusion is that these bubbles of gas are not CO2.

Ted[quote]

A couple of folks said that, but given the purity of the CO2(99.97% or so based on the test done at the place I get my gas from), the bubbles would need to dissolve much smaller, plus for the above reasons, such as time of day and rate of dissolving etc, it depends on when you make that observation.

I too observe the same things as you do, but I begin to see pearling on plants asap, then I see more and more bubbles later not being dissolved and I see higher DO levels with this method.

Something is making the plants produce more O2 thus grow faster.
The main cause appears only to be the CO2 delivery method.

The tank has been cranking and producing much higher O2 levels over two weeks now.
Regards,
Tom Barr

[jonathan11]

Tom, or anyone, can you mention a good diffuser disc to use, and possibly address the cleaning issues that seem to go with the discs? :gw :D :D

[stcyrwm@adelphia.net]

Tom, or anyone, can you mention a good diffuser disc to use, and possibly address the cleaning issues that seem to go with the discs? :gw :D :D

I'd like to know what folks recommend too. Someone recommended this one on another site:

http://www.aquabuys.com/miva/merchant.mvc?Screen=PROD&Product_Code=j_co2_diffuser

[Tom Barr]

Those are junky IME.
I prefer ADA, Azoo, and a few others that have a suction cup with it.

Regards,
Tom Barr

[stcyrwm@adelphia.net]

Those are junky IME.
I prefer ADA, Azoo, and a few others that have a suction cup with it.

Regards,
Tom Barr

Couldn't find Azoo diffuser. ADA costs about $80. Is there a less expensive route or is that just the going price for the quality? Aquatieco ozone/oxygen diffuser seems like the best deal at $55.00......

[stcyrwm@adelphia.net]

Tom,

Do you think this technique might open the door to help solve some of the limitations in a DIY CO2 situation? Or do you think DIY will have the same problems producing enough microbubbles as it does consistently staying over 30ppm??????

[Tom Barr]

Well it sure helped my DIY issues using the Venturi diffuser.

My DIY tanks did better than most CO2 gas tank folk's tanks.

Azoo is sold by Aq eco also and a number of other MO places.

Fairly cheap a good diffuser it seems.

Regards,
Tom Barr

[stcyrwm@adelphia.net]

I can't find an Azoo diffuser on Aqaticeco anywhere. I did search and went through a hundred items but no Azoo diffuser. I googled and I come up with zip. BTW what does MO stand for? Can anyone point me in right direction?

[matpat]

Here's a link for the Azoo diffusor: http://www.aquaticeco.com/index.cfm/fuseaction/product.detail/iid/3608/cid/4017

[stcyrwm@adelphia.net]

Tom,

You're not talking about the "Azoo air curtain" diffuser are you? It's the only Azoo diffuser I can find. Doesn't look like much but I think they carry it at Aquatieco also, it's just not listed as an Azoo product on their website.

Thanks, Bill

[stcyrwm@adelphia.net]

Here's a link for the Azoo diffusor: http://www.aquaticeco.com/index.cfm/fuseaction/product.detail/iid/3608/cid/4017

Thank you........

[reiverix]

Well I got home from work and it was purely spur of the moment but I'm going to give this a go. I hunted out my Azoo diffuser that's been dormant for about 10 months, and gave it a bleach dip to clean it out. My old setup was an external reactor hooked up to an external filter. It works fine but I like tinkering if it's easy :) .

Two things I quickly noticed. Firstly, I had only ever used the diffuser with DIY and was amazed at the bubble stream coming from compressed CO2. Secondly, I had to actually turn down my bubble count from around 4bps to 1.5 bps. I'm currently monitoring the fish and CO2 content. So far so good. To be honest I'm not expecting immediate miracles or anything like that, but if I get the same bang for using less CO2 I'll be a happy planter.

[Jay]

I really enjoy the reading, concepts, and experimenting with things I learn on this forum, but rarely post. I had an experience yesterday that I just had to pass on.

For the past two+ weeks I have been experimenting with the concept of micro bubble misting with CO2. I am using an old diffuser in conjunction with my venturi-modified reactor. The results have been dramatic, even the algae are negotiating unconditional surrender. The diffuser is old and frail and a new Azoo or Eheim is cheap enough I thought I would order one and make it a permanent part of my CO2 system.

Have any of you taken this concept on the road yet? WOW!

I ordered the diffuser from a fairly well know plant source (that will remain nameless). When the equipment did not arrive in a timely fashion, I called them to see what the problem was. I was put on the line with their CO2 “expert”. He immediately tried to sell me their super deluxe reactor. I declined and told him I already had one and wanted the diffuser. He asked why. I told him I was experimenting with micro bubble misting to improve plant growth among other things. He then proceeded to “T” off on me. The concept was the most “Stupid” thing he ever heard. What “idiot” gave me this idea? A visible bubble is a waste of CO2 no matter what size. On and on, about what a scam this was, I could not get a word in.

I finally got to ask if he was going to send my stuff. He said NO he was out of inventory. He also said that he thought he had several hundred in house but they were all gone.

Curious, I remarked. Just credit my account and I’ll move on. I wonder where they went?


Jay

[matpat]

For the past two+ weeks I have been experimenting with the concept of micro bubble misting with CO2. I am using an old diffuser in conjunction with my venturi-modified reactor. The results have been dramatic, even the algae are negotiating unconditional surrender. The diffuser is old and frail and a new Azoo or Eheim is cheap enough I thought I would order one and make it a permanent part of my CO2 system.

Do you have any pics of our venturi modified reactor???

I played around with my DIY reactor by adding a Kent Turbo Venturi to the intake and it quickly dropped the pH in my 75g about 0.3 in 10-15 minutes without increaseing the bubble rate.

The Turbo Venturi works well without a reactor also but the Quiet One pump I used is a bit too loud for my taste.

[Tom Barr]

I really enjoy the reading, concepts, and experimenting with things I learn on this forum, but rarely post. I had an experience yesterday that I just had to pass on.

For the past two+ weeks I have been experimenting with the concept of micro bubble misting with CO2. I am using an old diffuser in conjunction with my venturi-modified reactor. The results have been dramatic, even the algae are negotiating unconditional surrender. The diffuser is old and frail and a new Azoo or Eheim is cheap enough I thought I would order one and make it a permanent part of my CO2 system.

Have any of you taken this concept on the road yet? WOW!


I did not mention this idea to folks just sitting in my room one day "thinking", I did the method and saw the results first, then thought about it.

Folks that try it see, then they can squawk about why it works.



I ordered the diffuser from a fairly well know plant source (that will remain nameless). When the equipment did not arrive in a timely fashion, I called them to see what the problem was. I was put on the line with their CO2 “expert”. He immediately tried to sell me their super deluxe reactor. I declined and told him I already had one and wanted the diffuser. He asked why. I told him I was experimenting with micro bubble misting to improve plant growth among other things. He then proceeded to “T” off on me. The concept was the most “Stupid” thing he ever heard. What “idiot” gave me this idea? A visible bubble is a waste of CO2 no matter what size. On and on, about what a scam this was, I could not get a word in.


Well, I guess it's true then, I am very stupid and this person is obviously highly intelligent.

Funny, folks said that before when I added PO4 to my tank well over 1ppm and high traces and used tap water and used 30ppm of CO2 and suggested not using test kits and how to cure most species of noxious algae...........

I'm glad I am on the other side of the fence, as long as it's the right side. I have a great deal of practial experience and approaches to this, not all science, many seem to forget that. I'd rather be right than going with the flow.

So Jay, what do you think about the method?
Not the theory etc, but the practical aspects?
Do you think it's helped and would be helpful to others?

I do and it's not some small subtle thing either.
I'm still getting data and set up for the experiment.
Hopefully I'll have it done this weekend.



Regards,
Tom Barr

[reiverix]

Tom, does the surface of your tank water build up with tiny bubbles? I mean millions of them. I feel like I'm suffocating the tank but everything seems fine.

[Tom Barr]

Do you have any pics of our venturi modified reactor???

I played around with my DIY reactor by adding a Kent Turbo Venturi to the intake and it quickly dropped the pH in my 75g about 0.3 in 10-15 minutes without increaseing the bubble rate.

The Turbo Venturi works well without a reactor also but the Quiet One pump I used is a bit too loud for my taste.

Still think I'm full of crap?

If it's wasteful, why does it work better?
I saw the same drop in a 180 gal tank's reactor when we put a venturi loop on it.

Pearling occurred in 1 hour instead of 3-4.
pH went from 6.4 to 6.1

No other changes, no flow differences etc since it's a sump reactor.

I keep telling folks like I did with PO4 and eventually it too shall come to past.

Regards,
Tom Barr

[matpat]

Still think I'm full of crap?
Nah, only about 3/4 full. If you were full of crap you'd have brown eyes ;)


If it's wasteful, why does it work better?
I think the only way it is wasteful is if you don't throttle back the CO2 since this is obvoiusly a more efficient way of dissolving the CO2. I am referencing my use of the Kent Turbo Venturi valve on the input of my external reactor. This of course assumes you have optimal growth ( which few of us do) before you do the modification! I have yet to try the diffusor method but I'm not sure I will given the results I got with the Turbo venturi. Similar cost for the turbo venturi as the diffusor.

I also made one of your powerhead venturi reactors for my 30g tank. It is giving me similar results. Riccia pearls in about an hour and actually floats the driftwood to the top of the tank. Granted, it is a small piece of driftwood but it is still pretty cool. Pretty good for two 36" ODNO flourescent tubes without reflectors! I never got those results from my external reactor.

The Rotala sp. "Vietnam" is literally covered in bubbles halfway through the photo period now. Never pearled that much before your venturi reactor was added! It looks like it's covered in snow...might make a nice Christmas type scape when that time of year gets here :)


I saw the same drop in a 180 gal tank's reactor when we put a venturi loop on it.
It definately drops the CO2 faster with the Kent's Turbo Venturi added to the input of the reactor. The Turbo venturi also kept the CO2 levels up by itself while the reactor was off of the tank for several hours while I made a venturi loop and waited for the Epoxy to dry. If my pump wasn't so loud, I probably would've left the reactor off of the tank!


I keep telling folks like I did with PO4 and eventually it too shall come to past.

I think folks just need to give these things a try and prove it to themselves! You can read all you want about something, but until you do as Nike says and "Just Do It" you'll never really know...the Diffusors, Turbo Venturi, and powerhead/viewtainer, are small investments compared to how much most of us already have in our tanks!

[fishface]

I am referencing my use of the Kent Turbo Venturi valve on the input of my external reactor. matpat, how exactly does the turbo venturi work and do you have a picture of the configuration?

[Jay]

So Jay, what do you think about the method?
Not the theory etc, but the practical aspects?
Do you think it's helped and would be helpful to others?


I see what I see, there has been a dramatic improvement in my tank, and I had thought it looked good before I started experimenting. The CO2 misting was the only change in my fert routine.

The downside is the verbal abuse by strangers when you try to explain it to them. :rolleyes:

Jay

[matpat]

Here are three quick pics of the Kent Tubro Venturi. The first pic is of the venturi itself. The CO2 input is on the Tubro Venturi.

The second pic is how I set it up in the micro misting mode using a Quiet One 1200 pump (~300gph at 0" head). Intake is at the lower right of the pump and the output is at the top of the venturi. It produces a fine mist of bubbles and since the pump's flow is adjutable it can be set to send the bubbles all around the tank or just up the back of the tank into the flow of the filter. with some flow rate adjusting.

The third pic is how I have it set up on a 1 1/2" diameter DIY PVC reactor similar in design to the "Ghori" reactor with a "Barr" venturi. This was designed for a lower flow canister (Eheim ECCO 2234) and is a trial that has not been in a tank yet. The reactor is designed to be used vertically underneath the tank. The input is on the right side (top) of the pic and the output is on the left (bottom) of the pic. The "venturi" hose is about 2" down from the top of the reactor and is connected to the output side of the reactor. Hopefully this will discharge any undissolved gasses from inside the reactor to the output side of the reactor. I may move it farther down the reactor if needed once I install it on the tank and let it run for a couple of days.

In my 75g the Kent Turbo Venturi was on a 2" diameter clear PVC reactor Without any bioballs inside. This was connected to a Magnum 350 filled with bioballs so hopefully the flow is close to the advertised 350gph. This allowed me to see how the bubbles were "misted" into the reactor and disolved fairly fast. I spent a whole afternoon playing with the venturi and clear reactor watching it dissolve CO2 and drop my pH.

Here is a link to Bernoulli's Principle along with an animation for venturi design that is pretty easy for us "common folk" to understand.

http://home.earthlink.net/~mmc1919/venturi.html

There are also a couple of mpegs on the advanced discussion page. I didn't understand the physics, algebra and calculus much but the mpegs help explain it a little bit better, at least for me :)

[Tom Barr]

The venturi loop needs to be placed further down, about 1/2 down the reactor tube housing.

You can feed the venturi loop back into the intake side of the Quiet one pump also rather the outflow from the reactor or you can feed the gas into the Kent venturi with a Tee from the main CO2 gas line.

In any event, you can see that there are many options here and these loops and venturis do help decrease the pH better than without.

This also extends out to the CO2 misting idea as well.

Whether or not you agree with anything I've said, this method will improve CO2 utilization and improve growth if you actually try it.

And this type of work specifically on CO2 will generally do much more than anything with NO3/K etc and subtle nutrient issues.

So it's not time wasted....nor cost much to play around with.

Regards,
Tom Barr

[Cornhusker]

:) tom,i was at our city hospital the other day and they have a 200 gal salt tank. i noticed a tube at the back of tank blowing out tiny mistlike bubbles that circulate around the tank.looks like a beautiful way to work on freshwater tanks. i don't know much about salt tanks,would something like this work with co2?the mist idea is a very good one. i have tryed it many times in the past but then using yeast ,cant get enough pressure to get mist going.right now i have a small pump below the reactor blowing what comes out over the tank. it works fairly good.someone should have a ceramic stone of about 2"x 8" to fit nicely at back of tank that is very inexpensive.a person should use some kind of a bubble counter and solonoid with stone idea,right? regards,cornhusker :) :)

[alexperez]

I got my 2 small Azoo diffusers yesterday and hooked them up. I placed the diffusers in the path of the water flow(2 lily pipes on oppisite ends, each being driven by an XP3 Filter). The tank started to get filled up with lots of micro bubbles pretty quickly. I kept every thing else the same so the only difference was the use of the 2 diffusers instead of the External Reactor.

It was running for a few hours (6-9pm) but I did notice the pearling pick up
a lot. I had just done a triming 2 days ago and the stream of bubbles from the damaged parts of the plants went from a steady stream of bubbles to a fast stream of bubbles.

Now to keep an eye on it for a week or 2 and see how the plants react.

[Tom Barr]

So based on your and now quite a few other folks, what is your opinion?

If you keep the same CO2 rate and assumed that all of the gas was being diffused in the reactor, how can you get better growth(eg more pearling and other obvious signs of better tank health) without it being the CO2 delivery in the form of a gas vs dissolved?

You can see after about 1-2 hours the gas mist is far more prevalent and the plants start to pearl sooner in the day(1-2 hours after the lights come on) and if you measure the O2 levels, the O2 is also much higher.

Folks have said I'm wrong (I'm not:-) but you can see the observations, you can test it yourself and then see if you think those bubbles are really some other gas(they aren't) and the other issue=> there is no research on this issue. That is what I am doing right now and ruling out each issue step wise and building support for the theory.

In the meantime, folks have reported better growth, more pearling, less algae using this method.

So whether you agree yet or even care about that, you can still try this and see how well it works.

My data and method looks very good and supports the theory at every turn so far. I should finish and get it out later this weekend.

Regards,
Tom Barr

[reiverix]

What can I say. Based on this technique it means my bolbitis is actually pearling. Seems too good to be true but I can't deny my eyesight. My anubias doesn't pearl, which to me anyway, means it must be true pearling on the bolbitis. If it was just O2 bubbles then they should be covering the anubias also. Does this make sense?

[Tom Barr]

Yes it does, it's rare to see Anubias pearl but I've had them do it but mainly late in the day, Bolbitus I've had pearl like mad.

Also, Bolbitus is a very covetted plant and slow growing in most tanks, but I grew it like mad in my 55 for several years using the internal CO2 reactors on this site and they always [pearled like mad and grew very fast.

Growth = better growth than merely pearling alone without the associated growth that goes with higher rates of photosynthesis.

With time, folks can see the increased growth and you can also measure the O2 levels of the method vs dissolved alone.

Regards,
Tom Barr

[reiverix]

My bolbitis was a slow grower until I added a powerhead to give some flow around it. It exploded into life after that and I actually had to end up selling some. Never thought I'd see the day when I had too much of the stuff. LFS paid quite well for it too :) If my anubias start pearling my heart may stop.

[Tom Barr]

You can grow Anubias very easily emergent.
Mine does grow well submersed though.

Bolbitus will always be in high demand at the LFS making it a good trade species.
It's also a nice dark cool color that makes many species of fish look nicer.


Regards,
Tom Barr

[IUnknown]

Tom ran into this old post tonight. Didn't seem to make sense to me, so I was wondering if you had any updated insite to the reactor vs. diffuser issue. If the plants maximume uptake for Co2 is 30 ppm why would it matter if it comes from liquid or gas? When you say more oxygen, was this measured, or just eyeballed from the bubbles. how would you tell the differnence between Co2 bubbles falling on leaves and O2 pearling?

[Tom Barr]

DO meters work great for deteriming the difference in growth via plant production, it's the standard in aquatic biology.....

So the pearls are not we measure directly, it's the actual O2 in the water.

For this to work that way I've described, sense or not, the O2 levels much higher and the CO2 relatively the same based on the water's pH/KH.

The tank replicates with higher O2 may have lower CO2ppm, but not the reverse.

The hypothese is that tanks with CO2 mist will have a higher rate of plant growth(and production of O2 which is easily measured) than tanks without (everything else being provided on equal terms, eg dissolved CO2).

You can run the mist around the tank real good, then determine a relative CO2 ppm.

Next, try the 100% dissolved in the reactor at the same CO2 ppms and measure the O2.

You need a control for each test and relatively similar plant biomass/species etc.

I'm busy killing weeds and making huge tanks at the moment.

Watch the bubbles float around sometime from a diffuser. See how long they persist. CO2 does not dissolve instantly.

Even if mixed with other gases, the CO2 is expelled at a much higher concentration than the measly 30ppm.

So the CO2 can diffuse rapidly as a gas into plant, much faster than as a liquid [aq] phase.

Even at 380ppm that is typical air concentrations, and the rapid diffusion in air, we see enhanced growth of plants at 1500ppm.

You can see visibly the growth and pearling difference in your tank.
I'll get around to testing it and see what I can figure out miore clearly and look into it more.

Might be awhile still, but heck, no one else does these types things so there's no pressing rush either.

Regards,
Tom Barr

[IUnknown]

Tom wrote:
"The only way to add more than 100% ambient levels is through plant production."

What about injecting O2? I still have to read most of the other threads on this subject but was curious as to the conclusion of the "Co2 actaully being O2 bubbles" issue. It seems like the best way to disprove that would be to run the diffusser in a tank without plants (maybe this was done?). If the DO meter measures an increase in Oxygen levels then this would show that the Co2 bubbles are actually being filled up by O2 as the Co2 diffusses out. The idea is that the Co2 bubbles would be sucking Oxygen from the surface of the tank to over saturate the tank(were else would the O2 come from?). This would explain why the bubbles persist more later in the day as the tank is saturated with O2.

The other issue that I'm not convinced about is 30ppm being saturated enough to slow down the rate of diffussion. This thread did a pretty good job of disproving that idea,"CO2 Solubility Experiment - Photos, Video.....Evidence! " (http://www.plantedtank.net/forums/general-planted-tank-discussion/21776-co2-solubility-experiment-photos-video-evidence.html) . I guess you could connect a ph meter to a computer to see if the absorption rate changes at all. If it doesn't the Co2 would be a line in a ph vs time chart. It would be a bell curve if 30 ppm slowed down the saturation rate.

I've got a difusser in the mail to see how things improve. Regardless of whats actually happening the extra O2 is good for feeding bacteria, etc. Interesting stuff, I'm glad you have a thick enough skin to deal with all the attacks Tom, the hobby would not be going anywhere otherwise.

[Tom Barr]

Tom wrote:
"The only way to add more than 100% ambient levels is through plant production."

What about injecting O2?

Well yea, but I'm the only person that seems to have done so to date.
Going back about 4 years ago.



I still have to read most of the other threads on this subject but was curious as to the conclusion of the "Co2 actaully being O2 bubbles" issue.


Well I can tell you this much, they are wrong unless the bubbles rise up from the plant. O2 would have to cross that boundary layer, much like the slowed rate of diffusion from the surface layer intereface.

You know..........just like why the gas exchange rate is 10,000 times slower in liquid and air? That goes out the window when these same folks want to argue in favor of O2. CO23 will go into solution fast, but not one of these folks shows how CO2 and O2 goes _out of solution_ and into a gas phase.

That is key since they claim that the gas in the bubble changes rapidly.
they claim it changes from CO2 in a few seconds (some suggest instenanous!) to O2 or N2 gas.

But it takes time for the gas to come out of solution and into the microbubble.

As that time passes, the area, the boundary layer around a apheron will have a higher level of CO2 than the water adjacent to it.
That's the other part they have not considered.

A micro pH probe could show this.
I might be able to get one at the lab.




It seems like the best way to disprove that would be to run the diffusser in a tank without plants (maybe this was done?). If the DO meter measures an increase in Oxygen levels then this would show that the Co2 bubbles are actually being filled up by O2 as the Co2 diffusses out. The idea is that the Co2 bubbles would be sucking Oxygen from the surface of the tank to over saturate the tank(were else would the O2 come from?). This would explain why the bubbles persist more later in the day as the tank is saturated with O2.


I've run diffusers in tanks without plants, I was studying algae growth responses to CO2 and O2 at elevated levels.

I don't think there is enough O2 removal to detect anything significant if this occurs, which I don't think it is.




The other issue that I'm not convinced about is 30ppm being saturated enough to slow down the rate of diffussion. This thread did a pretty good job of disproving that idea,"CO2 Solubility Experiment - Photos, Video.....Evidence! " (http://www.plantedtank.net/forums/general-planted-tank-discussion/21776-co2-solubility-experiment-photos-video-evidence.html) . I guess you could connect a ph meter to a computer to see if the absorption rate changes at all. If it doesn't the Co2 would be a line in a ph vs time chart. It would be a bell curve if 30 ppm slowed down the saturation rate.


But the video shows nothing about what the gas is actually.
you andf everyone esle that's kept plants over the years have seen the increase time the CO2 microbubbles persist later in the day, these are not from plants, you can place the CO2 ADA diffuser right out in front, have the current blasting the mist around and see this over and over again.

The video does not address the microbubble, it does address the CO2 in a reactor tube which is a different case.



I've got a difusser in the mail to see how things improve. Regardless of whats actually happening the extra O2 is good for feeding bacteria, etc. Interesting stuff, I'm glad you have a thick enough skin to deal with all the attacks Tom, the hobby would not be going anywhere otherwise.

There's a simple thing, I know they are wrong, so I don't care as long as the attacks are not personal.

I'm not particularly certain what the gas is yet in the reactor tubes as they build up over time, but I can find out what it is made up of.

Thing is, no one esle will ever do that.
I ask folks to, but they are more interested in arguing Tom Barr is wrong than actually engauging in doing any work. At least Ted did some work and put it up on the web. :p Which is a lot more than I can say for others.

I have some other thing I haver tio do and finish up before I can get to that question just yet, but for now, a simple DO meter and the treatement/control will tell you if the plants grow faster or not with the method.

I'm not so sure about Ted's trail either.
I want to go back and make very sure this is actually the case.

I tested O2 in the reactor tubes much like Ted did for CO2 and O2 does not dissolve anywhere near the same rate, O2 and N2 are very insoluble in water.
These are the two best candidates for the other gases.

Ted did not test O2, I did.

So that's one gas in the reactor tubes we can rule out.
I have N2 at work, so I can test that one also but it's very insoluble and we can predict the rate it dissolves.

Now what about knocking N2 and O2 out of solution?
This is different than getting them to dissolve.

Reactors, unlike diffuser stones, have what precisely?
Generally they have a place for the bubbles to degas.

They have those bioball media which are designed for high flow degassing. This degases and then reabsorbs again.

But............I also see the gas form in my internal CO2 reactors which have no such degassing media of any sort.

The large bubble forms daily.
With or without the venturi running also.

The gas is purged also due to the burp holes in the side.
So it's not all build up like in the in line versions.

Why would the gas in a solution degas there and not else where?

There is a lot of unknowns so far and the results from the O2 meter suggest there is something to this and we can watch those microbubbles, folks can speculate that they are no longer CO2, but not one of those folks will ever get around to showing it is or is not with any certainly.

I cannot say that O2 will dissolve that fast into a microbubble, nor N2.
CO2 does dissolve much faster than either of these gases. It has to go across a gas/liquid boundary layer to do so, same with CO2.
So I cannot see how these rates can be the same, we can watch the micro bubbles come right out of the disc that we know is 100% CO2 and they don't disappear.

Apparently when the shoe is on the other foot....now they do not respond........funny how that works.:rolleyes:

Regards,
Tom Barr

[Professor Myers]

"It is an issue of delivery and in what concentration(100% CO2 gas)."

I'd like to test the purged false gas to identify the waste components, but I'm guessing that would vary depending on individual water chemistry so it may be a mute point ...?

The larger point being that the waste gas needs to be cycled out !

I also wonder if the ambient Co2 micro bubbles degassing aids in a better o2 balance ???

Mi Dos Centavos, Prof M

[Tom Barr]

Well a micro bubble of air, pure air, will presist a long time, it's mostly O2 and N2 gas, but there's CO2 in the bubble as well.

For a bubble to presist at it's stable concentration and not degas into solution, the solution and the apheron must be in equilibrium.

Partial pressures in the apheron microbubble = partial pressures of the solution gases.

So what I stated orginally was that the CO2 gas would presist longer in a solution that is 30ppm vs 3 ppm.

The microbubble will have 30ppm at least(or more being time dependant) and an air bubble will only have 1-3ppm CO2 depending on the ambient levels.

The micro bubble that is not dissolved will have a higher concentration of CO2 than tank water that is 3 ppm of CO2 vs 30ppm.

I think this is much more along the lines what I meant to say to begin with and gets around some of the problems I had eailer with the dissolving rate.

The rate is still the same, depending on the KH, but the end point is different.

The micro bubble is left with 30ppm (end of day) vs 0-3ppm (start of adding CO2 during the day).

The other issue is flux due to the boundary layer(bubbles bob right through those well) and the flux coefffiecent is 10,000X faster for a gas than a liquid.

So even if the microbubble equilibrates with it's surrounding water, it's still better at delievry of the CO2 gas to the plant.

Later in the day, the CO2 microbubbles will become higher or at least = to the surrounding water which by then is 30-40ppm CO2.

Regards,
Tom Barr

[ringram]

Tom,
I should have read this ages ago. When I saw you in person about a year ago, you showed me that diffuser disk to give a very fine mist and I should have just used it right then and there. Instead, I made a PVC reactor and while I'm getting Co2 mixed into the water, I didn't realize that the plants can't use it as easily. That would explain why I've been constantly battling different kinds of algae, particularly green spot on plant leaves and glass. Furthermore, some plants just won't grow and simply wither away and die. All this while my Co2 levels are testing good (ph - 6.4, 5 DKh), which apparently is more of a false-positive.
Are you saying to add a diffuser disk in conjunction with an inline reactor, or instead of? Is it just a simple airstone disk that you would find at the LFS, or something else? With the amount of lighting that I have and the amount of ferts that I add (EI), I'm now convinced that this was my problem. That's what I get for not heeding your advice!

[Tom Barr]

I think I am closing in on the reasoning why this works better and it also shows why the ADA products, particularly the misting amplifies the growth of his tanks so well.

I did not think about the theory I presented about "mist" but it would lend credence to the notion of less CO2 but higher growth using mist.

You can try either methods, a hybrid reactor/disc or pure disc.
I use venturis/disc and disc and reactors and disc methods.

I think over all the venturis/disc work best, but these are better suited for large tanks.

Small tanks, the disc alone, larger tanks: reactors.

I will say the Aquatic magic disc I recently got: WOW!!
great product, like the ADA beetles except 5x cheaper.

See ebay site.

BTW, I'm redoing the Albany Aquarium for Guy this Sat.
I'll be using the AM disc.

Should be fun, I'll use the African root for the hardscape.
Oddly, I've never used this wood in any scape.


Prof M, did you test the Gas that's purged?
I'm lacking time and other things at the moment and will not get to it.
It is one of the great mystries yet no one has ever tested what it might be.
I'm thinking O2 and N2 mainly.

Regards,
Tom Barr

[reiverix]

Using the mist method, my plants definitely pearl better with good circulation. I noticed this after giving my 75g jungle an overhaul and making it a bit more manageable. Purple cabomba and rotala magenta was pearling so much I could barely make out the leaves. Quite a sight.

So as an experiment I waited until CO2 switched off and let all the microbubbles from the diffuser fizz out. So now the only bubbles in the tank were true pearling. I gently shook the cabomba and a few other plants to clear them of bubbles. Well after 10 minutes it was bubble city once again. Hardly scientific but I think I can conclude that it was true pearling and not microbubbles from the mist method landing on the plants.

[VaughnH]

Now that was a neat experiment! It does seem like a foolproof way to prove that the bubbles, whatever they are, are coming from the plants. And, oxygen should be the only respired gas, I would think. Otherwise, one would have to argue that a supersaturated gas in the water was coming out of solution on the leaves.

[Tom Barr]

Plants keep expelling O2 at night , you need to wait longer, they also have stores of "lacunae", aerenchymanous tissue, holds lots of air, and they gets slightly pressurized. When the O2 is pumped out, these relax and there is less pressure.

These may act as a store house of O2.
In anaerobic hydro soil, this is a very good thing.

Basically leftover pearling.

But yes, you can assume there is no CO2 left/mist from the diffuser.
That would be safe to say.

Regards,
Tom Barr

[Professor Myers]

Sorry Tom, I'm a bit slow...:rolleyes: I'll see If I can set up to either preserve/contain the gas for test, or direct the waste for a chromatagraph. I don't enjoy the same access to equipment these days. I can have a friend do a readout at the plant, but I reckon it will likely vary as much as the source ? In which case the results are subjective, and not particularly viable. O2, and N2 were the pat answer from the plant. Depending on the refinement O2 waste varies, and N2 remains fairly stable. Prof M

"Prof M, did you test the Gas that's purged?
I'm lacking time and other things at the moment and will not get to it.
It is one of the great mystries yet no one has ever tested what it might be.
I'm thinking O2 and N2 mainly. "

[Professor Myers]

Does waste gas actually provide any vital stimulation for receptors ? and what would happen if you taper off envioronmental stimulation ? :confused: Prof M