CO2 after water changes and an experiment

[Tom Barr]

Many suggets that the pearling we often see after a water change is due to air/O2 and other gases such as N sticking to plants and is not true O2 pearling.

There are a few ways to address this to see if it is in fact "increased growth" or just sticky bubbles (This arguement has merit and must be addressed).

One way to test and see is:

I recently tried something interesting with hair grass.
I took replacement water that was at equilbirum with air and tank temp.
So no air/gas, etc is going to come out of solution and stick to anything.
Sound reasonable? There's no high CO2 etc from the tap water here, the buckets full of water have been sitting for 48 hours and the tank and room temps are equal. Note, the replacement water is RO, no other nutrients are present.

I drained the water down to exposure the hair grass to the air.
I slowly refilled the tank with the low CO2 warm water.

Observation #1:
The plants had no bubbles upon filling the tank.

Observation #2:
After 15-30 minutes, the plants began intense pearling, very intense.
As intense as you could possibly imagine.
Anyone could tell and see this massive difference.

Nutrient limitation is ruled out due to EI and ADA aqua soil(4 months old).
Light is at 300 micro mol, plenty high for good photosynthesis.
Plant health is good.
No fish, no snails to speak of.

Why would the plants not have bubbles after the water change, then formation occurs 15-30 minutes later?

The only reason I can figure out to such a degree that influences plant growth like this is due to exposure to air for 5 minutes.

What is in air that's not at high levels in the tank?
CO2 in the gas phase.

This shows/strongly suggest that aquatic plants can dramatically increase production and growth if they are supplied with a gas phase of CO2.

It's a simple test and the observation #1 shows that it's not due to degassing tap water etc, it's due to the gas phase exposure to air.

Mimicing this with CO2 mist is a generalized concept for that theory.



Experiment no#2:
I have a DO meter that measures O2 levels in water.
O2 levels are strongly correlated with plant growth and production in aquatic ecosystems. O2 levels are used to determine productivity(true pearling) in a quantative manner in research science.

This allows me to measure the rate of pearling or the rate of total plant and/or algae growth due to a treatment.

So if I have a tank that's limited due to PO4, then add PO4, I see dramatic pearling increase and can verify this with my DO meters as well, often times by about 30-50% growth increases if the PO4 limitation is fairly strong.
So this is a fairly useful tool used to measure plant growth in our tanks!

Few plant aquarist have these devices, I think only old George Booth was about the only person besides myself on the web that uses them for aquatic plants.

So I tested the before and after O2 levels at the same time I did the water change above. I had 7 ppm(100% a tad over) before and 11ppm after(t= 2 hours) or about 160%.

60% higher plant growth is something anyone should be able to "see".
People huff and moan about various things to improve their plant growth, yet CO2can increase the growth by 10X easily or 1000% faster.

It is far more critical in most cases than NO3 or PO4 etc.

Yet few test to see if the water change is really adding a gas phase of CO2 that increrases the plant growth, instead arguing it's just degassing water.

As far as I know, this is the first demostration without a O2 meter to show and confirm that pearling in this case was due to gas phase exposure to CO2.
The backup with the O2 meter offers more support for the contention as well.

If folks see intense pearling after a water change, and then for the remainder of the day(do a large water change early in the day), it generally means it's due to the tank not getting as much CO2 to the plants as it could.

CO2 mist side steps adding a lot of CO2 gas into solution, rather, it leaves it in the gas phase. I've confirmed CO2 mist increasing the O2 levels by 50% without no change in bubble rate. Simply switching from a mist injection from a reactor with 100% dissolving efficiecy(All the CO2 is dissolved).

I'm not happy with the CO2 measurment, so comparing the ppms is harder to do since the error overlaps between both treatments, but the bubble rate of CO2 delivered to both treatments remained the same.

Once I get good CO2 measurements that I can be very confident about, then I can move forward and argue very strongly for CO2 mist.
Many have already seen the dramatic effects of the mist method.
Many complain there's too much growth and that such pearling is a disstraction.

But others like it and I personally do as it kills off algae as well and I like to push the limits of systems till they break or crash. I'm weird that way I suppose:p

Regards,
Tom Barr

[2wheelsx2]

Nice writeup Tom. I must admit, I've often wondered about the gas bubble theory also. I get intense pearling after a water change, especially from some Riccia remants (annoying pest) that I am still cleaning up after experimenting with it as a foreground plant. I don't take water straight from the tap. My water is taken from a 30 gallon storage container for natural dechloration (our supply only uses chlorine, and very little of it). Our local water is mostly from rainwater runoff and snowmelt, so it's very low in TDS, so there is not much in the way of nutrients added to the water. I see the same thing that you have described in experiment 1. I get the most intense pearling for about 6 - 8 hours after the change.

Prior to getting pressurized CO2, I used to only have pearling after a water change (I had DIY CO2). Now, with pressurized, and using your misting method (diffuser arranged under the outlet of my canister), I get significant pearling after 2 - 3 hours of lighting, every day, but never as good as after the water change.

[JoeBanks]

This assumes that during a water change, plants are exposed to air.

What about plants below the water line? They are not exposed to gas phase CO2, but seem to pearl more after a water change regardless.

Why not repeat experiment #1, draining the tank to just above the hairgrass, thereby not exposing the plants to air.

If the theory holds, there should be no increase in pearling.

This topic really interests me because of odd observations made on my tank recently. As i posted previously, to combat murky water, I've been injecting air into my system at night. A couple of days ago, I upped the air from 1 bubble every 3 seconds to 2-3 bubbles per second.

At 8:00 am the next day, before the lights came on, and before the CO2 came on, the plants were already pearling like mad. It was not just sticky air bubbles coming through from the air pump. I could see streams of bubbles coming from the plants. This was without light, so there should have been no photosynthesis. There must have been CO2 gas in the water just from the air pump, but how can plants produce O2 without light? I can reproduce this effect very easily just by adjusting the amount of air injected into the system at night.

Makes me think that there may be more to pearling than just photosynthesis.

[Tom Barr]

I've done that Joe, but have left that out, forgetful I suppose:-)...... good point.
Now I think about it, it does not pearl nearly as much (although there is a good amount of pearling still).

This seems to give credence to the idea that exposure by gas phase will give you an increase in pearling/O2.

But a temporary spike of CO2 vs a continous observation like with mist seems to be the real question. You can easily get a nice pulse of growth, but be unable to maintain this same growth rate/momentum later.

If we do back to back water changes each day:
Say 60% one day and then observe, then repeat again at 60% and observe, we can likely make some more conclusions.

We can rule out weekly organic build up(we can also add purigen or Activated carbon etc and this also improves growth is many cases).
This needs ruled out as well.
Converting more of the nutrients to the inorganic phase may help increase pearling.

But the real issue is how long can that intense pearling occur?
Every day for a week or two?

What is it about a water change that causes that intense pearling?
Is it really the degassing water?

I do not think so really, in some cases perhaps.
We can blast CO2 for an hour at high levels and notsee the same effect.
So CO2 alone cannot account for it entirely it seems.

As far as night time, well, there's a lot of bacteria, and murky water really shouts out high loading, wood, so so plant growth here and there, so so CO2, the pearling is likely due to respoiration by bactera, that normally consumed the O2, reducing the O2 in the tank.

Water changes = more CO2/less organic loading.

More organic loading: more bacterial consumption of the organic matter=> less O2levels in the tank= more murky looking water.

Large water changes and more CO2 ought to correct and improve things for you.
You can also try purigen or AC.
Regards,
Tom Barr

[a1matt]

It's a simple test and the observation #1 shows that it's not due to degassing tap water etc, it's due to the gas phase exposure to air.

First off I should state that I haven't done any specific experimentation just general observations over the last year or so of water changes...

I have a non CO2 tank and after a 50% water change (straight from the tap, not letting it degass) I get water bubbles everywhere, but they pop once and are gone. So in my mind they are not pearling.

Any plants that were exposed to air, have a tendency to produce bubble, pop, and produce more, which I take to be pearling. I've also observed that the longer the exposure to air the more the likelihood of pearling.

I also get pearling after the waterchange on my vallis when I have accidentally 'torn' one of the leaves. I get a mixed feeling from this - 'oh bugger I tore the plant :eek: ' and 'cool, loads of bubbles :D '

[Brainman]

First of all, greetings everyone, I`m a new member, but is never to late...

In my case, pearling is much more intensive, after water change, but my TAP water has pH 7.5-7.6, kH readings are about 6, so i have to tnink, that my tap water has poor CO2 levels.

I use PMDD, with some PO4, K2so4, KNO3, MgSO4 x 7H2O, and trace elements, so i think that nutrients are not problem for better pearling.

In my aquarium i have pressurized CO2 sistem, DIY reaktor with powerhead and i have pushed CO2 to about 40mg/l, light is 2x MH 150W for some 350 litres, but i have much better pearling after water change. I think that CO2 is not limit in my aquarium, or my calculations are not correct, or plant can collect carbon better from tap water?

Great site...Keep up the good work !!!

[TTKarl]

I do have to add that after pruning my anacharis i do see massive amounts of bubbles escaping from the cut stem. I don't see how this can be pearling. Could the pearling you see after a water change be the same bubbles i see escaping from a cut stem, either do to the change in pressure from the changing water level(like on a plane when your ears pop from expanding/contracting gasses) or from damaged tissue from excessive movement from the water change?


Just a thought.

[Tom Barr]

Here are some notes:

I tend several client tanks every week.
One is a larger tank, with high light, 28" deep.

The upper part has Java fern. Lower parts, other species that are much faster growing, thus more likely to pearl.

After the water change, there is no pearling in the first few minutes.
Then, without fail, the places with the highest light intensity begin to pearl first(10-20 minutes after the water change).

This pattern is consistent.
The faster growing Rotala does not pearl and is not close to the higher lighting.

Thus one might think this suggest that the Photosynthesis, driven by higher light=> pearling, rather than excess air accumulation, or sticky degassing bubbles.

My experineces with degassing bubbles contends that they appear almost immediately after the water change, and they stick to everything/everywhere in the tank regardless of lighting......that is if you accept that they are degassing bubbles, which clearly in the Java fern/Rotala case, I do not see how they possibly could be.

This observation and rational suggest that it is not degassing, it is light driven photosynthesis.

Degassing bubbles should stick to everything regardless of location and orientation.

But this is not observed in this tank or my other tanks.
Also, one can do daily water changes and see this same effect repeated every day and a higher growth rate.

The other way is to run an O2 meter and measure the Oxygen, which is higher on water change days but you could argue that the bacteria drain more as the organic matter accumulates through the water etc(adding AC or Purigen etc could act as a control and remove that fraction though).

So it's not just what is in the water, it's also exposure to the air itself.
If it was merely excess gas taken into the plants, you also would not see localized pearling relatable to the lighting.

It offers up more proof towards my contentions about water changes and adding CO2 via gas phases.
I know it's not sticky air bubbles and degassing water in the above cases.
I know what I am seeing along a lighting gradinet is photosynthesis.

I saw that pearling along the lighting gradient(light and pearling are proportional) and knew right away what it meant.
It answers the question in these tanks about water changes, exposure to air etc.

I can also drain and fill at the same time and thus change almost all the tank water with no exposure to air also........so that would give me a tank with a large water change and no decline in the water level, and see if the same patterns exist.

That's next.


Regards,
Tom Barr

[reiverix]

The reason I started using a mixing barrel is because after water changes the pearling was so fizzy, it caused certain stem plants to uproot. It was really annoying. Now I mix my change water for two days with a very large powerhead. I still get more pearling after a water change but nothing like when it was straight out the tap. I know for a fact my tapwater has 15ppm CO2.

[Tom Barr]

Too much pearling:) ?
I reduce my light if I want less growth.
I've recalled with some substrates or shallow depth, that plants would not stay down. Riccia often would pull loose after the water changes if not well trimmed etc.

I think the exposure to air in the non CO2 planted tank is part of the issue about why it might be bad every week or two etc. And in some cases, much less of an issue if the tap have low CO2/you allow the water to sit over night etc prior to changing the water.

We have sonme serious issues in evaluating tap water changes due to the many variables Tap water has.

Some has high Copper
Some has high CO2, some low CO2
Some folks use cold tap
Some have PO4 sometime of the year
Some have varying conditions in the tank

Hard to say as folks seldom test their tap water every time they do a water change:cool:




Regards,
Tom Barr

[defdac]

Now when you mention this there was a time when I always changed my water with one hose (siphon) coming out of the tank and one with fresh water into the tank - without altering the water level.

No pearling. We have < 0 ppm CO2 in our tap due to hydroxide treatment, and very low nutrientlevels.

Since I started to do ordinaray wc:s where I lower the surface to just a couple of cm from the substrate the "after wc champange" have started again... Hmm...

[Tom Barr]

Now when you mention this there was a time when I always changed my water with one hose (siphon) coming out of the tank and one with fresh water into the tank - without altering the water level.

No pearling. We have < 0 ppm CO2 in our tap due to hydroxide treatment, and very low nutrientlevels.

Since I started to do ordinaray wc:s where I lower the surface to just a couple of cm from the substrate the "after wc champange" have started again... Hmm...

Yes, lime softening removes the CO2. So that make's sense. Some water companies recarbonate the water and lower the pH, essentially adding CO2 to the tap.

If not, there's not going to be hardly any CO2, a high pH and very soft.
Most blend the softened water with the un softened water in partial lime softening methods. This way they can avoid recarbonation.
But the tap still has very low CO2 though but decent pH and they can produce more soft water, btu not super soft.

The hydroxide also will mess with the pH/KH as it adds some OH alkaninity, which will make it seem like you have 200ppm and fish are fine and plants grow well.
Limestone regions will often do this and have CO2 tap water issues with aquarist.

Try this, time the exposure to air, and use a spray misting bottle to keep the plants moist/splash water on them every 10 minutes etc.

Try for 5 min, then for 30min.

You can clean the tank really good while the tank's low(not a bad idea anyway!).
If you watch, and add black cloth blocking the lights on one side of the tank, then refill, you should see dramatic pearling only on the side with the light.

That will essentially prove it's the exposure to the air.
You will need to replace the tank water without the exposure to air also as a control and see how the black cloth effects the plant's pearling.

So this may be a good reason to do large water changes:D
Even if the CO2 is low in the tap.

It'll also give a standard of what optimal growth and pearlign is, so folks can try and get that same effect all week long rather than for a day or two.

And one thing that it will show more support for is that the idea behind the gas phase in CO2 mist, is well supported here. => 30-40ppm of Dissolved CO2 in water is not the maximum growth attainable. We can grow things even better with CO2 mist.

My personal goal is not max growth rates, it's max growth for lower light. I prefer to use less light to throttle growth rates as well as judicious plant choice. This provides the best mangement and the most stable method for a tank.

But knowing all this helps to focus the needs of other folk's goals, who may not want this.

Regards,
Tom Barr

[dcheese44]

I don't use a misting method, I use an in line reactor with a dedicated pump. I do get pearling later in the day, similar to water changes but it seems to take a while to develope that pearling. With large water changes I get a lot of pearling and it takes about 20-30 minutes. I called in a couple of favors to borrow a DO sensor, but, Tom how did you use the O2 levels to calculate CO2, won't that depend on plant concentrations and types of plants? I am curious to see where the CO2 concentrations settle out. And in the end if I should need to make a change with the method of delivery. I don't have any problems(major) with algae. There's a certain level of algae, that I don't care much about.

[dcheese44]

Sorry, this is an aside...
I tried to post a picture to show it but, couldn't, I guess the format is wrong. Which format do i need?

[Tom Barr]

You do not use DO to measure CO2.

O2 levels are correlated with plant growth.

So say a tank with one CO2 method produces say 110% saturation of O2 at a given temp at 8 hours after lights are "on".

The same tank with CO2 mist produces this same level after 3 hours of lights on and then rises to 140% at 8 hours after the lights are on.

Note, this is the same tank, flow characteristics, just one day you do the normal CO2 method, then the following day the CO2 mist method.

That difference in the O2 levels and the timing is due to the CO2 mist effect.
As long as the nutrients levels are non limiting(eg: EI dosing) and light are the same in both cases, then the rather large change in O2 production by the plants is due to CO2.

Plants grow based on light, CO2 and nutrients.
There's plenty of water obviously so that's not considered.

Tank changes between the light/nutrients/plant biomass/current/temp are minimal in the same tank between one day vs the next day.

You can run a control to a see if you wish there as well.
I know what the control does and it tends to stay pretty stable in terms of O2 production difference in 1 single day, they do not change much.

so if you change the CO2 method between one day and the next day and see a huge jump in the pearling and O2 levels, then that is telling you that's very likely the CO2.

O2 meters measure just that, not other gases.
O2 is the best measure aquarist have of actual plant growth althougnh dry weight and a very accurate scale would be nice and correlation of wet/dry weight sand plant parts etc would be nice and nutrient extractions etc.

See the "Phytometer" MS word doc here for more info.

===============
So using this same method with the O2 meter: remove say 70% of the tank water and not expose the plants to air. Save this same water. Add back to the tank. Measure O2 levels.

Next day do the same thing except remove 90% of the tank water and expose the to the air. Wait 5-15" min mist with some water to prevent dessication. Refill with tank water. Measure O2 levels afterwards over the same time frames(not one discrete point, rather, several for both treatments).

I had 28-52% increase for O2 for the CO2 mist method and about 40-60% for the air exposure treatment. That's a lot more growth increase than folks normally ever see.

That's why mist causes too much growth and too much pearling for many folks.:rolleyes:

Formation of O2 bubbles also forms on the top portion next to light where photosynthesis occurs 1st in larger tanks . If it was mere degassing, we'd see bubbles everywhere, but I do not only on the plants closest to the lights and then with time, the plants progeressively farther and farther from the light source.

The plants are exposured for 1 hour and are misted till the refilling neat the top and less so near the bottom.

So is it due to the light distance or the air exposure?
I'm not sure but it seems reasonable to suggest that some of both. How much pearling growth will we get out of a ceertain time of air exposure?

Seems like a little for little exposure.
Or a lot for a longer peroid.

That sounds reasonable.
Without doing a lot of measurements, it'll be hard to say.
Even then generalizing would be tough.

Still, try this exposure to air for say 15" minutes and watch the tank.
Try it 2x a week for 2-3 weeks and see what happens to the tank's health.

It'll shoot through the roof.

My goal here is two fold:
Look at CO2/how the gas phases might be of use to us and to help folks with potential CO2 and algae issues get rid of it.

I noted that Cladophora and other species fo algae took a beating and stopped growing etc and some died off as a result of this treatment in a friend's tank.

It'll not help the algae, so it's worth a try and see the effects.

I trust most folks here can tell the difference between pearlign and degassed bubbles.

I'm not going to bother explaining this to other folks out side the BR. I just do not have the time.

Regards,
Tom Barr

[Brainman]

Sunday is a day for water change, so I changed water (tap water) in my tank without my lighting hood, because i had to repair my light (bad contacts). My lights were off, and after water change I saw outgassing bubbles in my aquarium without the lights over it, it look like real pearling from the plants. This was not real pearling, but this may be the reason for better and much more intense pearling after water change, outgassing bubbles in combination with real pearling ?

Turn off your lights, after water change to check your bubbles...

[Tom Barr]

Try this, turn the lights off a day first.
Then do it.

You have a fair amount of O2 still being given off if you turn the lights out before doing the water change. Look at where the pearling is occurring.
Then place the light back on and note where pearling occurs.

Regards,

Tom Barr

[Brainman]

I`ve changed water in my tank in the morning without my lights, then I started with one neon light 18w (only to be able to see what is going on)... I saw, that lot of tiny bubbles were created under all leafs, after water change. "Pearling" started from all my plants including glossostigma...Plants with wide leafs, released much bigger bubbles. Ludwigia repens released bubbles that look the same like pearling. After 2 hours "pearling" was almost over. Then I put back on standard 300w and I had to wait about 3 hours to see real pearling.

I think that water temperature is having great deal in pearling after water change.

Next sunday I will chage with cold(er) wather to see what is going to happen...

Misa

[Tom Barr]

I just did a new round of water changes and noted some bubbles of the glass in some of the tanks.

The issue is best resolved with a DO meter.
I did note that the time it took to form new bubbles was about 15-30 minutes after the lights where on. The water change really sent the pearling into overdrive vs any night time water changes I've done.

I think many have noted this, even Amano has said things suggestive of this.
He likes to dose and do water changes in the morning, when the plants are able to use the nutrients the most and are actively growing.

Regards,
Tom Barr

[Tom Barr]

I think a few things here might prevent some misunderstanding and doubt.

1. Make sure you can tell the difference between good vigorous plant growth vs mere bubbles on the plants. You should see better growth, less algae and importantly, longer persistent growth.

2. The other thing I've done and I know some of you have as well: knock the bubbles off after a water change. Wait 15-30 minutes, then look for bubbles.

3. I did 2# with the test hair grass tank. hat's the only plant in there, it does very Tell, no algae issues etc. You see a little pearling, not much, the plant really does not express a great deal and biomass in the tank is just the mat surface layer only.

I've been doing #2 for clients for many years, I do not like the look of bubbles on the glass, I like a nice clean look when I leave and have the plants growing like weeds. I always wipe the glass/acrylic down right away when I begin to drain the tank, before the water is all drained out, so that surface is clean when the water is filling later on.

I also fluff the tank good after and during a water change, Real good initially, get any detritus out of the corners, any muck, organic matter that should not be there out of the tank and netted up etc.

After refilling, I tend you swish a net around to get any leaves that might be loose, caught in the healthy plant beds/groups, any algae or muck of any sort.

Then I clean any bubbles that form and wipe the front of the glass and off to the next client I go.

I've stayed around and watched the bubbles form after this.
No bubbles reformed on the glass. Bubbles reform on the plants closest to the light first(10-20 minutes). Then progressed down into the tank.

Typically after removing/pulling up the organic matter, disturbing the substrate, O2 levels can plummet. Removal of the muck is good, after there's very low drain on the O2 due to bacteria trying to decompose all this excess muck.

This might play some role in tank's pearling better as well. Organic dissolved matter also plays a large role. I'm one of the few that discusses it.

Amano gives COD levels, which is a nicer, easier to measure parameter than BOD.
I have not done any, but I can predict they'd be much lower after a large water change and I'd be right 99/100 times.

A weekly sum total graph versus a single parameter(who knows when that measure was taken?) can tell you a lot more so please be critical on such data.

The other plausible argument for the bubbles afterwards if you do not have a DO meter/O2 test kit: The plants leaves act like a sponge with the gases, taking them all in and then releasing then slowly after wards.

Well, think about this...........
Now if it takes say 5 minutes to soak in the gas, how long does this plant keep bubbling off the gas?

1 hour? 4 hours? 8 hours of light?

Plants can take in a fair amount of gas and they store O2 in their aerenchyma for their roots, then any excess is piped out.

Algae reduction also suggest something else besides air alone is going on here also.

Many folks notice their tanks pearling like mad after a water change.
Now try this: see if you can stop or stunt this pearling via nutrients or CO2.

**Now you need not harm the plants over the long term either here**.
Just a day or two of no CO2 ought to do it.
PO4 deficiency will greatly reduce pearling also after about 1-2 weeks without much stress to the plants, some GSA and other issues might occur but not that much. Do the water change and note the difference. Give it about 4 hours, see anything happening?
You might aseea little pearling, but likely not that much.

Now, after the 4 hours, add some KH2PO4 after starving the plants a bit for PO4.
Wait 1 hour, now look?
What a difference.............

You may also use one single group of plants that normally never pearls etc, that you have troubles with etc to explore this rather than the entire tank.

I think the notion I am trying to show folks: we can amplify growth better/further/get more pearling/more O2 levels.

Is this a must for the hobby?
No!

Can it help folks and help the basic understanding of algae and plant growth?
Yes!

Is it a good clue that you might not have enough CO2 when the dramatic difference in pearling from the water change day vs the rest of the 5-6 days of the week you do not do a water change?
I think it does and can be generalized as such.

Regards,
Tom Barr

[livionakano]

I had 28-52% increase for O2 for the CO2 mist method and about 40-60% for the air exposure treatment. That's a lot more growth increase than folks normally ever see.
This numbers are separated and independent variables, there are an addictive effect or there is an maximum degree of increase? (if I do both methods, should I observe 28-62 + 40-60 % increase for O2?)

The exposure treatment could be compared to hydroponic Flood and Drain System, where roots are exposed alternatedly to air and hydroponic solution ?

So, would be better to start the CO2 mist some minutes before the lights on, for an additional increase in plants health? I am using a single timer for lights and CO2 solenoid valve.

Can be the same effect observed if we put a glass with air, inverted (like a bell position) and expose for some minutes the plants that are on the botton, or close to it, like carpets or anubias, and for this reason can´t be exposed to air during WC ?

Regards,

Livio

[Tom Barr]

I had not thought about using hydroponic root systems for the potential for storing O2 and CO2 etc.
Mainly just focusing on the shoot, as it's the part that does the O2 production.

The data just gives the ranges I measured over the same time frames on several tanks.

There is noit an additive effect.
I think exposure to pure CO2 gas ut of the water would produce the strongest O2 production afterwards.

Air would be second followed by the thick viscous medium of water with CO2 mist+ good dissolved CO2, then finally CO2 all dissolved with no non dissolved gas phase.

That's what I would predict anyway.


The goal here is not so much to have folks drain their tanks down to 95%, that's impractical with fish and other issues. It's the learn a bit more about how algae and plant production/growth rates are effected by O2 and CO2.

Few do much thinking about CO2, they would rather waste all their time on haggling over NO3 and PO4, or Ca and Mg.
Those are important as well, but CO2 is 40-50X more important in terms of dry weight biomass.

When we see dramatic increases in pearling, we should figure out a good way to measure that increase.

O2 meters are about the best measurement tool we have for that. But perhaps observations alone can help other folks.
It might not work, but we have to try:)

I think we still can see some evidence that the gas phases do increase growth and pearling with these methods not using an O2 meter.

One thing to think about is how might we be able to produce that much pearling and growth all week long and not just after the water change?
You need to see that intense pearling, health and growth first........then you have a max growth rate to compare to.

That is now your goal, the bar you set to achieve for your tank's growth.
You also should focus on CO2 if you use EI, EI rules out the nutrients leaving only the CO2 as the dependent variable.

We can deliver the CO2 a number of ways.
ADA and many other delivery in the gas and dissolved phase.
A combination of both appears to provide the best growth and what I would hypothesize.

So CO2 gas phase + dissolved would give the best results.

We are limited by practical matter with exposure to air or pure CO2 gas for brief periods, but we might observe and learn from those exposures and observations also;)

Many folks find that when they switch to CO2 mist, they have almost too much pearling, intense growth etc and algae makes a hasty retreat.
Other folks appear not to have much luck, but it might be they have not set the tank up right etc, not adding enough CO2, have other confounding issues with their independent variables etc.

Yes, it is ideal I would think to have CO2 come on about 1/2 hour before the lights come on. Then shut off about 30-60 minutes before the lights go off.

That way, as soon as the lights come on, the plants have plenty of CO2 and get going right away.


You might try the glass air bubble method to see.
I would also suggest looking at the DIY internal venturi diffuser I designed, it acts like the glass a little bit.

If you place the downward firing gas mist diffuser above a plant, it will grow very intensely compared to a similar plant on the other side of say a 4 ft long tank.

Now the pH will be the same throughout the tank mind you, but the growth will be different.

So the dissolved CO2 is fairly even, but the gas phase is the main difference in the treatments.

There are many designs you might try out here, but proving them will generally require a DO meter and relate that to growth rates.

Regards,
Tom Barr

[cousinkenni]

Hi Tom and others,

It is funny that I came across this thread for the first time today. Last week I was looking at my two 10g rotala tanks and I noticed a huge increase in pearling after doing my normal 90% water changes on the (left) rotala tank. Although this left tank pearls during the day, after a water change the tanks pearls like crazy. The right tank will also increase in pearling, but not as much because it already pearls like crazy. [by the way Tom, the one I was having trouble with (the left one) I ripped down, vacumed the gravel, cleaned the filter, replanted and now it is doing way better, still not up to its potential, but way better]

So to continue on.......I don't think this is actually due to CO2 in the water from the pipes because the water from the pipes is about 40ppm KH and a pH of almost 7 wich leaves the CO2 in the single digits (I will varify the CO2 content of the tap water as soon as I order some certified 4degreeKH water from Bill? for my drop checker.). I was planning on doing a negative control experiment next water change where I do the change about 3 hrs before the lights come on........If pearling occurs with the lights off then you know it is offgassing of other gasses dissolved in the water...........If I don't see the pearling within 15-30mins (about the normal time it takes to see the pearling with lights on) then I can assume that the pearling is due to one of two things: 1) exposure to CO2 from the water (unlikely see above) or the air (very likely as explained by Tom ealier in this thread).

The other interesting thing I have noticed is the left tank which actually has more CO2 dissolved in it than the right tank doesn't grow as well and doesn't pearl as much as the right tank, which has less CO2 (I determined the CO2 content by testing pH of the water in each aquarium and comparing the colors side by side; and by using the drop checkers in the aquariums with homemade 4degree KH solution). How could this be you ask? Well although the tanks are identical in every detail including the CO2 diffusor used, the left tank's CO2 diffuser doesn't work as well as the right tank's diffuser. The diffusor on the left realeases way bigger bubbles that go straight to the surface whereas the right diffusor releases tiny tiny bubbles of CO2 that go everywhere in the tank.

When I first setup both tanks I was wondering why the left tank was doing so bad........each tank had the same number of CO2 BPS. When I compared the tanks pH's side by side the left tank was always bluer. To compensate for the lower CO2 I started raising the BPS on the left tank which still didn't make the plants pearl like the right tank. Now I am at the stage where the left tank actually has more CO2 and it still isn't doing as well. This has to be due to the fine mist of CO2 that the right diffusor produces.

After I do the water change experiment this week I plan on switching the CO2 diffusors to see if this make a difference. If the left tank all of a sudden starts going crazy then it is obviously the CO2 mist not just how much dissolved CO2 is present in the water.

Anyway thats my experience thus far.

On another note I am having a problem with the drop checker returning to blue the next moring......I already read posts in other threads so I am going to buy the calibrated solution and move the drop checker in a higher flow area to see if that helps. I am using the ADA idicator solution that came with the drop checker. If the drop checker is still green the next moring I am going to raise the filter outflow to create more surface agitation. The flow rate is rediculous for this tank as it is (no glass on top, a fluval 104, 10g tank, and the outflow flows straight across the front of the tank)


Ken T.

[Tom Barr]

The idea behind this experiment is to get folks thinking about such things.
To show that testing CO2 and O2 are important and have profound effects on growth.

Some cases will not lead the person to conclude this effect is real, but with good measurement tools, you can get a better comparison of these various tank differences and address such issues.

The goal is really to have a better understanding of CO2 and O2 production in our tanks and address many of these assumptions.
We must try these assumptions and see if they are reasonable

Without testing and thinking about it in this context, many will never see/learn more about it. Given it's critical role, that would not be wise.

I have the equipment and measurement methods available to do the work and test.

Most aquarist do not and remain, at least some, unconvinced.
I am trying to address methods that might allow them to test and rationalize it without buying DO meter and spending a lot of time measuring things.
There are trade offs with this less sophisticated method, but also some nice effects in the routine(lots of pearling).

Regards,
Tom Barr

[cousinkenni]

Hey All,

So I did that experiment (negative control) I was talking about in my previous post:

Water Change + No Light = no Pearling

I checked my Tap water using my Drop Checker with home made KH4 solution) and it stayed blue indicating a lack of CO2 in my tap water (I just got my KH4 reference solution from Bill right this moment so I will do another experiment tonight to double check)

This means that Light is required to induce the pearling meaning that the bubles aren't from degassing of CO2, O2, N2 or methane from the water. The bubbles are deffinately being produced by the plants in the presence of light (Photosynthesis). On top of that, since the source of CO2 isn't coming from my tap water, it must be coming from the exposure to air (in concordance with what Tom has been saying!).

Ken T.

[Tom Barr]

I often wonder about this type of stuff when I do it and wonder and really hope others can demonstrate it also. Then I know I'm not a nut.
Well, perhaps I am, but it's nice when folks actually try such things out and see for themselves. I get awful tired of critics that never do jack:rolleyes:

They say today's mighty oak is yestderday's nut that held it's ground.
Would not be the first time.

I'd try it again though.
Think about all the other things you may have overlooked.

My question is less that there is an effect that increases O2, rather, how much and can this level of O2 production be maintained and for how long?

Could we do this daily if there's a problem with growth/algae etc?
I do not like chemical treatment of algae, I think amplification of plant growth and manual removal methods are best.

Some have disagreed, but I think this offers a new tool to help folks see what the potential is and also to help beat back algae at the same time.

Also, make sure you time the exposure to air.
How much is optimal here?

Such questions are harder to answer and you need to measure O2 levels over time to get a feel for that.

So a 10 minute exposure might yield a 10% increase for 2 hours in the O2 production rate at the peak(sort of a sharp peak with along tail after), while a 30 minute exposure (this would require misting the plants with water to prevent them from drying out) might yeild say 15% for 3 hours etc.

What is the maximum we can squeeze out of the plant for a given light level?

Those are much more interesting questions.

Regards,
Tom Barr