Adding Co2 to tank


New Member
Jun 5, 2021
Long Island, NY
Hi Everyone,
I just purchased a GLA regulator and I'm in the process of adding Co2, I also purchased a Glass drop checker.. My question is what's the best way to start adding Co2 without overdoing it.. I have a 29 gallon planted tank. I don't use an airstone and at one point I lost a fish and it looked like there might not be enough oxygen in the tank so instead of using an airstone I pointed the return (spray bar that goes the length of the tank) to the surface to have better surface aeration and that seemed to help with the oxygen but now my PH is around 8 and I wanted to lower it. I know adding Co2 will lower PH but what's the best way to try to equal out enough Co2 for the plants and enough oxygen for the fish. Thanks, Gus


Super Moderator
Staff member
Lifetime Member
Jun 20, 2016
I would suggest setting things up so that fish have enough oxygen (no labored breathing) then adding enough CO2 for your target ( say 30ppm). Adding CO2 at 30ppm won't drive O2 from the water, in fact during the light period if your plants are healthy it will help increase via photosynthesis the O2 concentration way above what it would be with an airstone.

Start slow , increase a little every day checking the drop checker and fish behavior throughout the day. At a starting pH of 8 it is very likely that your KH is also very high. To significantly reduce the pH it might be worth to deal with the high KH first.