Well I was just making sure as that can normally be the problem. If you check out the planted tank a lot of the people have been experncing deaths some one lost 30! yes 30 danios in one due to co2. Someone else lost 3 discus and there worth like 200 dollars each.
5 gallon,natural planted tank with 1 betta.
20 gallon community tank.
6 gallon guppy fry tank.