API aquarium salt is made from evaporated sea salt and is a must-have for your aquarium. AQUARIUM SALT promotes fish health by improving gill function, making it easier for fish to breathe. It also provides essential electrolytes that fish need to reach peak colouration and vitality. These electrolytes may be lost each time you perform a partial water change, and will need to be replenished. API Aquarium Salt provides electrolytes freshwater fish need. Electrolytes are essential in Freshwater fish helping with the uptake of oxygen and the release of carbon dioxide and ammonia through the gills. If there is a lack of these electrolytes in the fish, they can start to develop health issues. API Salt is made from evaporated sea water and provides these electrolytes the fish need to reach peak colouration and vitality. Salt improves their gill function, making it easier for them to breathe and helps to reduce stress The salt does not evaporate and is not filtered out so it should only be added with each water change. Use the salt when starting a new aquarium, doing water changes and solving fish problems. Add 1 tablespoon for every 20 Litres of water Specifications API Aquarium Salt 16oz (454g) Treats 404 Litres (88 Gallons) Add 1 rounded tablespoon for every 20 litres of water.