Aquarium Salt is pure salt (Sodium Chloride) prepared from evaporated seawater. It doesn’t have any additives like iodine, calcium silicate or anti-caking agents so it’s safe for freshwater aquariums. Aquarium salt is beneficial for your fish and helps improve gill functions, heal wounds, get rid of bacteria and adding essential electrolytes. Electrolytes help with oxygen uptake and the release of ammonia and carbon dioxide through the gills. Without electrolytes, your fish can experience serious health issues. It can also be used to treat some diseases, like fin rot and ich. But not all health issues will be solved by adding aquarium salt.