Aquarium Pharmaceuticals Aquarium Salt is an all natural salt, made from evaporated sea water, promotes healthy gill function, reduces stress and loss of electrolytes. Used to improve the efficiency of medications and reduce the harmful effects of nitrite. As A General Tonic and Stress Reducer: Add 1 rounded tablespoonful for every 5 U.S. Gallons (19 L), or 1/2 rounded teaspoonful for every U.S. Gallon (3.8 L) of aquarium water. To Enhance Tropical Fish Disease Treatment: Add 1 rounded tablespoonful for every 5 U.S.Gallons (19 L) of aquarium water. Note: Aquarium Salt does not evaporate, and is not filtered out so aquarium salt should only be added as directed with each water change. Treats up to 107 U.S. Gallons (404L) of fresh water.