text: Bought this salt for our 20 gallon fiddler crab tank and it works perfectly. It is maybe not the most cost effective salt additive; you can buy marine salt for cheaper. Folks seem confused about aquarium salt. API aquarium salt is NOT for brackish/saltwater tanks. It does not supply the necessary nutrients, minerals, etc. THIS brackish salt can be used for brackish or saltwater setups, although, as stated previously, not likely the most inexpensive option if you have a larger tank.