First day of CO2 and 5 tetras died :(
Today was the first day of CO2. Its a 30G new tank (3 weeks old). Ammonia 0.25, Nitrites 0, Nitrates 5. I use 2X21W light. I had 8 Rummynose and 8 Neons and 2 cherry shrimp.
I set the CO2 at only 1 bubble per 2.5 sec. I set the light and CO2 to start at 1PM and when I got home in the evening at 6PM, 5 tetras have died but the rest were running around as if nothing had happened and not gasping for oxygen or anything.
Any reason why it may have died? too much CO2?