I wanted to ask for some advice on O2 levels with CO2 injection. I have only been doing planted tanks for a few months. Since I started I have been focusing on getting 30 PPM+ of steady CO2 and haven't paid attention to O2 levels at all. I originally set up my Fluval output about 6-7 inches below the water surface to reduce the loss of CO2. When I set up my new CO2 system on my tank I gassed my fish to near death. Luckily I caught it in time and used a power head with a piece of hose over night and they are all fine. I have read a few threads about people running air stones at night, and was wondering if people can give me feedback on this. Right now I moved the filter output to about 3 inches below the water surface to create some surface agitation, but no air stone yet. I am using EI dosing on both CO2 injected tanks, and the plants seem very happy with excellent growth and minimal algae issues. I am thinking that since the plants use O2 at night, it can only improve the overall health of the plants. Any advice would be greatly appreciated, I'm interested in hearing about peoples set ups, and how it effects the plants. Thanks.