30ppm CO2 vs 20ppm CO2

[Burr740 67]

Personally, and this is the case with all my tanks (both sand and soil tanks with KH ranging from 0-1 to 5-6) plant-wise I cant tell a difference in a 1.2 drop and a 1.5 drop. But I can tell a difference between a 1 point drop and 1.2. At a 1 point certain species start having problems and things overall dont do as well

Im also a big believer in consistency, up and down levels cause big problems which are likely rubisco related as @Yugang said. Especially if co2 drops down to a growth limiting level where plants start having to make up for it

In general I shoot for about 1.3, the fish I do have are fine at this level, not even sluggish in the daytime or anything like that. I also have skimmers on most tanks which make a huge difference, even more than surface agitation imo.

 

[GreggZ 17]

But I can tell a difference between a 1 point drop and 1.2. At a 1 point certain species start having problems and things overall dont do as well

Agreed and this is the key. People always say a 1.0 drop is the goal. But more is better.....but like you said to a point.

And the other problem is that people have so many ways of calculating that drop wrong. In the end Barr is right.....before you mess with everything else right take the time to get CO2 right. Makes everything else easier.

 

[Unexpected 4]

@Unexpected , have you indeed settled for a 1.0 pH drop for the tank that worked so well for you? From your article ("tank of the month") it is not clear what your degassed pH reference is?

Yes and no, during the competition set up, I introduced a fish which was sensitive to CO2 and had to back down to a 1 pH drop. Now, after gutting the tank I’ve had weird unpredictable pH oddities. I’ve started adding .6KH and now just drop the tank exactly 1 pH from the peak pH just before CO2 turns on. So, if it’s 6.5 right before CO2 on, I have the controller set to 5.5. We know from practice this isn’t true degassed but saw this suggestion on the 2hraquarist page and it works. I’ve tested going a bit further and that one fish will sip the surface.

 

[BigWave]

People do not take into consideration how CO2 is getting into the tank. Reactor, Diffuser, Bubbler etc. They all add CO2 differently or i suppose economically. Then there is the bubble mist inside the tank where the microbubbles attach to the plant leaves vs reactor and no bubbles at all argument. The type of reactor plays a role here too. They are technically called dwell time reactors for a reason. The longer the CO2 is in contact with water inside the reactor the better it gets dissolved.

 

[Yugang 5]

Yes and no, during the competition set up, I introduced a fish which was sensitive to CO2 and had to back down to a 1 pH drop. Now, after gutting the tank I’ve had weird unpredictable pH oddities. I’ve started adding .6KH and now just drop the tank exactly 1 pH from the peak pH just before CO2 turns on. So, if it’s 6.5 right before CO2 on, I have the controller set to 5.5. We know from practice this isn’t true degassed but saw this suggestion on the 2hraquarist page and it works. I’ve tested going a bit further and that one fish will sip the surface.

If you have a 1.0 drop from early morning (not fully outgassed), then from my experience with my tank you may well be at a 1.4 .. 1.6 from fully outgassed. It really depends on your tanks outgassing during the night, plus CO2 production by livestock, plants and micro organisms. Not unlikely that fish protest when pushing more as you say.

I bumped this thread, as I hoped that your top tank was at a modest CO2 ppm, but this seems not the case.

How to measure CO2 levels in an aquarium

Too much CO2 or too little CO2 in your planted aquarium? How else to achieve optimal CO2 levels in your planted tank? Why drop checkers do not always do a good job. This page explores all these issues and more.

www.2hraquarist.com

You may be referencing this quote:

"A general good range to target is a 1 full point pH change. So for example, if your tank's pH starts at 7.5, you would target a pH of 6.5 for when CO2 hits saturation during CO2 injection. This would give you about 30+ppm of CO2 for tanks where the KH value is between 1 to 10 degrees KH."​

This should be read as "if your tank's fully outgassed pH starts at 7.5" for the science to make sense. Referencing to early morning pH does not say anything about CO2 ppm.

I remember you mentioning drift in dKH , if this is still happening it will affect the work of your pH controller and your CO2 stability. There is unfortunately no way around that when using a pH controller.

 

[Art 173]

Are you using a controller? If so it's easy to dial in. Go to 5.02 and observe for a day or two. If still showing signs then back off to 5.07. And so on. At some point you reach a level where both fish and plants are happy.

This is exactly why I use a controller. I'm not chasing a number but it allows me to target a number for consistency. As @Burr740 said, consistency is important.

I don't know about all of you, I get uncomfortable when people start throwing around fixed numbers in this hobby. One point pH drop or 30 ppm CO2 or 1.4 pH, etc. I do believe in very general rules of thumb to start your tweaking but I think each one of our tanks will tell us what the right balance is.

I think it was @plantbrain that said to increase CO2 until your fish get uncomfortable then back off a bit. This tends to be more of my thinking. Observation becomes the most important part of dialing in CO2. To make it consistent, that is when gear really helps.

Great points all over this thread. Thanks @Unexpected for posting the question.