The HC is very unlikely to survive if you stop the CO2. The other plants may make it, but when I have done that I have had lots of plant problems. Usually the other plants get leggy, the lower stems tend to rot, the leaves get much smaller, and the stem plants may break free from the substrate to attempt to migrate to better growing locations (which is doomed to failure!). I had the best success when I just started the tank over as a low light tank.
I agree with the part about the leaves of the HC getting smaller with no CO2. But, thankfully, I have never experienced anything like you describe when switching from CO2 to non-CO2. (With the caveat being that my tanks always have soil and qualified light.) But I am also more conscious of giving the HC more light than one might recommend when not injecting CO2 - around 65 PAR. The truth is, NOBODY, has ever recommended this to me in these terms… I wish they would have :-)
Tropica has a nice article
explaining the energy trade-offs when gathering light and CO2 and how the plants can effectively spend more of its energy gathering CO2 if it is not also light limited… and vice versa. Ultimately, they conclude that limited light and rich CO2 is the best combination for optimizing plant growth and managing a planted tank. But you can also draw other conclusions regarding non-CO2 tanks in that you don't want to co-limit both the light and CO2. Better to give a bit more light so the plants can spend more energy fixing carbon. The study's results with riccia showed that there was a six fold increase in net growth when only increasing the light compared to the case when both light and CO2 were limited.
I've always taken this to heart and will commonly tell people to increase
their light on their non-CO2 tanks when I can tell that the tank is limited in both CO2 and light. But a lot of people are gun shy with increased light on low-tech tanks: because of the threat of algae. But the common language to avoid this problem is: PAR. It's too bad that most people don't speak it.
It's ok, Hoppy, we don't have to rehash why people don't speak it… I get it. I'm just tired of that argument. A fair amount of hobbyists drop amazing cash on pH controlled CO2 injection and other tank gizmos, but they balk at the price of a PAR meter when it's less expensive than automated CO2 injection, and the one thing that could help them more in more situations.
Ok, thank you for the compliments and input. Going to have to do something about the name thing...(:-)
So I appreciate the help and suggestions but I'm going to chicken out on the switch!
It is a nice tank… and as the saying goes: If it ain't broke, don't fix it. The challenge of converting to non-CO2 would be a good one, but personally I wouldn't go into it blind. But given that your tank is a soil tank and that you have some vague idea of what your PAR is, I think you'd have no problem turning off the CO2 and not adjusting anything else. But I'd bet $10 that your "bright room" would only contribute about 2-3 PAR when your target should be 50-60 PAR :-)