Hey guys. I was hoping you could help me with some understanding regarding a few comments by Takashi Amano in his book "Nature Aquarium World" Book 1.

Pg. 174

"To find out how much CO2 the plants are consuming, compare the pH levels of the morning and the evening. The pH should be at its lowest level in the morning (before turning on the light) after a night of fishes respirating oxygen and expiring CO2, and at its highest level in the evening (before lights out) after a day of plant absorption of CO2 and discharge of oxygen. The greater the difference between these two values, the greater the consumption of CO2, and therefore the greater the health of the plants."

Question 1: What are your thoughts on this statement, is it still accurate?

I just got my drop checker a week ago (using kH 4 reference fluid) and over the last week I have dialed in my CO2. The plants response (pearling) is amazing and I know that I am on the right track. I'm glad I took it off the pH controller. However, as the day progresses my CO2 indicator goes from green to light green. It doesn't hit yellow, but the CO2 level is increasing as the photoperiod progresses.

If I combine his statements and my experience, it looks as though I am actually overdosing carbon (via CO2) and I should decrease my bubble count.

Question 2: Do you agree?

Question 3: Should I change my CO2 bubble count as to maintain a constant green color, while seeing a pH increase during the photoperiod? If this is actually possible to achieve ....

Question 4: If my CO2 level fluctuates from 30 to something higher, does this fluctuation still lend itself to a higher probability of the appearance of BBA? Or, is it just a fluctuation on the low end of the scale that lends itself to BBA?

Thanks so much!

Regards,

Well, it assumes that there is no limitation via CO2, light intensity is also not mentioned. As anyone that understands even basic photosynthesis and what every student learns in basic biology class: light starts Photosynthesis and that produces sugar and O2.

To make sugar, you need CO2.
To fix and reduce CO2, you must have light.

More light= more CO2 fixed.

Does this have a limit?
Of course.

That said:
Consumption of CO2 does not indicate greater health, just more Carbon being fixed. A stable non limiting CO2 level would suggest a steady supply, which allows for maximum growth, which would imply greater "health".
You can test this easiy and prove it to your self and use an O2 probe.
You will get higher O2 levels(thus more CO2 fixed) with steady state non limiting CO2 vs allowing the CO2 to drop.


Nothing wrong with this at lower lighting.
At higher lighting it starts to be more of an issue.


No, if you assume that limiting CO2 will produce more growth, you are wrong

Rather obvious.

However, some might suggest otherwise and stray from the path of photsynthesis and what defines "growth"- more biomass/more plant and faster growth rates.

If you want say less growth but still healthy, try less light.
Then the CO2 is not limiting still.

When you limit anything, that will decrease growth.

Some confuse that decreased growth with "better" because it slows things down and makes it easier to manage.

We can slow things down via light, CO2 or nutrients.

Light(lowering) makes the most sense.
Here's a lower light ADA tank:




While accurate in terms of KH/pH, there is a delay of about 1-3 hours here.
The color differences are variable due to the eye and the accuracy is not bad per se, but it's not precise either.

You can add a bit more CO2 and be a little yellow eariler when the plants are growing/"waking up" and then have it decline later.

You can also shut the CO2 off at about 8-9 hours in. Plants are pretty much done after that. It's the first few hours that are the most important.

Yes, it's possible by adding a lot of CO2 and degassing a lot of CO2.
Since the in/out of CO2 is far more than the demand from the plants (you waste some CO2 this way, but it's cheap), the CO2 level is stabilized.


No BBA is induce near as I could ever tell, it's when the CO2 drop under higher light, and if it starts out very low initially for the first 1-2 hours (a very common problem), this causes a wide variation.
That confuses the plant and helps the algae get that foothold.

Too low CO2 for a given light level and too little at the start of the day, I'd say you are fairly safe near the end of the day with too little CO2, but it's a good point to try and keep it steady all day but less critical as you decrease the light intensity.

ADA, other folks are not going to go all into it in detail, namely because they lack the expertise in algae culture methods and inducement, let alone taxonomy.

It's more complicated than the nice little tidbits you read about, the whole world is for that matter, but we like a nice simple package, so folks latch onto that.

We all do it to some extent.

Regards,
Tom Barr

How so? What happens? Is it just that an excess CO2 level could potentially hurt the fish?


Indeed. But my concern is more the fluctuation in pH and the role that plays in my system (outside of plant growth). I'm talking about lowering my CO2 level but staying within my drop checkers "adequate range".


This is interesting ... I will indeed experiment with this one.

Thank you for your assistance,

Simple, more luight = more CO2 demand.
At lower lighting, you depend on supplemental CO2 less.


pH flux is not detrimental to fish, plants algae etc due to CO2 alone, CO2 is not an osmolytic component, like adding say KH is.

Basically you can change the pH by 1 full unit rapidly with CO2, but doing the reverse and riasing the pH one full unit with baking soda will kill them.

You can try it and see for yourself, many/most folks do massive water changes and replace with tap that's at a full unit higher pH.
Fish have no issues there.

As far as what is "adequate", well, I certainly can argue and suggest that no added CO2 is "adequate", but it'll certainly slow growth way way down.

I'm not clear on what is meant by "adequate".
Limiting?
Non limiting?
10ppm?
Enough where you do not get algae but still get amplified plant growth etc?

Why not limit the amount of lighting, then you have a lot more wiggle room with CO2?

That's the safest most logical approach, especially for folks that are historically plagued with CO2 related issues.

Works like a charm.


Try adding more CO2 early on, then let it taper. Get as much in there ASAP.

Plants are not really going after the NH4 that was released by decay/fish waste etc all night, so adding CO2 early when the lights come on seems like a good reason to pump as much as you can in asap earlier. That drives the plants to use up the NH4 rapidly that built up over the night time.
Rather than the algae..............

CO2 drives uptake on many things, so if you reduce it, or have high then low, then high, or start out real low, then build late in the day etc, you can still get algae.

So stable CO2 is key.
Or non limiting.

The limiting levels are much lower at lower lighting.

Why some suggest adding lots of light and limit the CO2 down to say 10-15ppm is beyond me, less is better but they do not apply that to light

ADA limits light, then they add it, after the CO2 has built up, then it tapers off after it's been sucked out.

So at low light, the CO2 can build up, then ADA adds a noon time burst, about 2-4 hours, (3 hours on average), that drops the CO2 down, then the high light goes off after the plants have had their high growth peroid and the CO2 comes back up again at lower light and then off a bit before the lights go off.

The tank acts as "reservior" for the high CO2 built up at lower light.

But, do we need the high light at all?
No.

That way the CO2 is stable and non limiting the entire day length, providing more wiggle room. Adding a 2-3 hours high light peroid will let you get away with things pretty well CO2 wise, but trying to do it for 10 hours will cause issues, or not adding enough in the start.

High light, poor CO2(plants are limited), and NH4 all encourage algae.

Lower light, higher CO2, and lower NH4 discourage algae and help plant growth.

You do the math

Regards,
Tom Barr

I wonder if these orientations have some place in tanks without solenoid valves, or with yeast CO2 injection, when this data about changes in pH, might be somehow more useful than in tanks with "non-limitating CO2".
Seems to be an advice that is a bit old, nowadays.
I am now following the two timers suggestion, starting CO2 1 hour before lights on, and stopping one hour before lights off, with DIY CO2 reactor and non-limitating supply of CO2, achieving much more pearling and plant growth.

From the same Amano - Tropical Fish Hobbyist Magazine Vol LV #6 february 2007 - "Balancing Light and CO2 in the Nature Aquarium":

"We define the standard value as the pH value just before the light is turned on in the morning (before CO2 injection begins for the day), after sufficient aeration throughout the night. If the pH value mesurement is higher than the standard value four or five hours after the start of the CO2 injection, the amount of CO2 injection is insufficient. If the measured value is slightly lower than the standard value, the amount is adequate. If the measured value is much lower than the standard, the amount is excessive."

Regards,
Evandro.

Those are awfully general terms

So general that you cannot really infer much, I think that issaid that way to allow for a lot of wiggle room rather than giving precise data or showing that they did a lot of testing and stats to show a specific range.

It does suggest that the first 4-6 hours are the most important for adding CO2.

Regards,
Tom Barr

Indeed.

Using the terms below. My standard morning pH value is 7 and it drops to 6.4 in the afternoon. Test kits questionable, as usual. Mine is Tropic Marin, less questionable than Tretra's. I assume, more questionable than La Motte. I cannot find those to by in my place.

Whether a 6.4 pH is slightly or much lower than 7 is something that I don't know, but since my KH is 3 (Tropic Marin again), I have about 35 ppm CO2 at 6.4 pH (according to a CO2 table). Too much if other acid stuff did not contributed to lowering the pH, as I have seen in other threads, but looks to me ok if I take other acids into account (besides, I use my fish as test kits ).

Generally speaking, again, it makes sense to me having lower pH after CO2 injection. After all, if we wanted to have a higher pH we wouldn't inject CO2 at all. Would we?

Regards,
Evandro.

If we just wanted higher pH we would increase the KH, and go ahead and inject CO2, so the plants could benefit from it.

I understand the play on columns and rows in the CO2 table, but would the increased KH be slightly or much higher than the standard, before CO2 injection, KH?