Is There a Difference Between Freshwater Aquarium Salt & Marine Salt?

Fish hobbyists frequently use salt for both freshwater and saltwater (marine) fish species, and there is no difference between the basic salt used in freshwater aquariums and the salt used in saltwater aquariums. In fact, because the salt used in fish tanks is pure sodium chloride, non-iodized table salt, kosher salt or pure rock salt can be used in place of standard aquarium salt in the right amounts.

  1. Maintence Levels

    • Catfish and other slick-skinned fish do not tolerate salty conditions of any kind.

      A common use of salt is for maintenance levels for freshwater and saltwater aquariums. The recommended amount for a saltwater tank can vary depending on the species of fish and plants that are living in the tank. A basic salt content level for saltwater tanks is 1.023 (+/- .002) specific gravity (density to water). However, a basic ratio for freshwater tanks can range between1 tsp. of salt per 10 gallons of water to 1 tbsp. of salt per 5 gallons of water. Although live freshwater plants cannot tolerate salt in any amounts, there are some species of freshwater fish that thrive in low-salt conditions such as live bearers and brackish water fish.

    Medicinal Levels

    • Only experienced fish hobbyists should attempt to use medicinal salt ratios on freshwater fish.

      Salt can also be used as a medicine to treat freshwater fish parasites and illnesses. Therapeutic amounts of salt in freshwater tanks are generally 1 tsp. of salt per 10 gallons of non-chlorinated water. When using salt to treat parasites such as ichthyophthirius (ich) and anchor worms, a ratio of 1 1/2 cups of salt per 10 gallons of water is advised. When using salt water as a tonic "dip" for freshwater fish, select salt ratios that result in a specific gravity of 1.009 to 1.023.

    Types of Aquarium Salt

    • Pure canning salt is also safe to use with fresh and saltwater tanks.

      The main concerns for using salt in aquariums are if the salt is fine enough to completely dissolve and if the salt does not contain chemicals such as nitrites, iodine or potassium. Commercially prepared aquarium salt mixes can include minerals in levels that are safe for specific fish species. However, there are also special blends of salt mix that mimic the pH range and mineral ratio for specific bodies of water across the globe such as reef mixes for corals.

    Considerations

    • For maintence levels, start with small amounts of salt and gradually increase it.

      When selecting fish for a freshwater tank, consider if there is a preference for fish that thrive in low-salt conditions, in high-salt conditions or in brackish water conditions. And, when performing a partial water change, only replace the salt ratio for the amount of water removed. For instance, if using a teaspoon of salt for every 5 gallons of water and 5 gallons of a 10 gallon tank are being replaced, only add 1 tsp. to account for the newly added non-chlorinated water. Be cautious of over salting fish that are not accustomed to salty conditions. And, if fish begin showing signs of stress, such as gaping or bleeding, reduce the amount of salt per gallon.