Laticauda;4846489; said:Try to keep your nitrItes below 1, and add one teaspoon of salt per gallon. The salt will out-compete the nitrIte in the fish's gills, which enables them to "breathe." Otherwise the nitrItes prevent O2 from getting into the fish's blood, which causes nitrIte poisoning, also called brown blood disease, due to the lack of oxygen in the blood.