Marine vs. Aquarium Salt

What Is Marine Salt?

• Marine salt is a product used in marine and brackish aquariums to simulate a saltwater habitat. Marine Salt is both the name of a trademarked brand of water additive produced by Seachem as well as a more general term used to describe any additive designed to turn regular tap water into saltwater. Marine salt contains sodium chloride (NaCl) as well other elements commonly found in ocean environments.

What Is Aquarium Salt

• Aquarium salt is basic sodium chloride, or NaCl, which is also the basic chemical makeup of standard table salt. However salt sold as aquarium salt does not contain additives like iodine and calcium silicate often found in table salt, as these additives can be harmful to fish. Aquarium salt is designed for use in freshwater aquariums. Aquarium salt, unlike Marine Salt, is a nontrademarked term used to described this basic sodium chloride and is available from various aquarium supply companies.

When to Use Marine Salt

• Marine salt should be used to create a suitable environment for saltwater fish. It should never be added directly to a tank with live fish in it, but instead it should be mixed and aerated before the introduction of fish. For a marine aquarium, follow the manufacturer's instructions to create a saltwater mixture with specific gravity between 1.023-1.027. If creating an environment for brackish-water fish, mix the marine salt at half strength to create water with a specific gravity between 1.002-1.007. When maintaining the tank, make sure to check the salinity of the water before adding more saltwater mixture. As only water tends to evaporate, you will likely only need to add fresh water, and not saltwater, to top off the tank.

When to Use Aquarium Salt

• Aquarium salt is recommended with the use of all freshwater fish, with the exception of Corydoras catfish, which do not do well with any sort of salt in their water. In freshwater most kinds of tanks a small amount of aquarium salt will help to make tap water closer to a natural environment. Salt is beneficial for sick fish because it helps to replace their sodium and chloride ions; it can also inhibit fish from absorbing toxins like nitrites and has been shown to prevent parasites. The salinity of freshwater aquariums should be kept very low; if your fish become stressed or sick it is recommended that one tablespoon of aquarium salt be added for each 5 gallons of water.