API Aquarium Salt 936gAPI Aquarium Salt, made from evaporated sea water, provides these essential electrolytes fish need to help them breathe easier and remain healthy in their new surroundings. Electrolytes are essential for the uptake of oxygen and the release of carbon dioxide and ammonia through the gills. A lack of electrolytes may cause serious health problems. Aquarium Salt does not evaporate, and is not filtered out, so it should only be added with each water change. Care should be taken when using salt with live plants, as some plants may be sensitive.