Aquarium Salt Mixes – Choosing the Right Salt for Your Tank

Choosing the right aquarium salt mix to add to your tank can be can be a confusing process, especially if you’re new to the hobby. But, it isn’t as complicated as it may seem, you just need a little background info to get you on the right path to choosing the salt that is appropriate for your set-up.  

Salt in Freshwater Aquariums

Adding salt to a freshwater aquarium is not a necessity, but it is used by many aquarists as a treatment to add electrolytes to the aquarium water, and as both a stress reducer and a parasite deterrent. Basic Aquarium Salt is not the same as the formulated mixes used to make a brackish or saltwater aquarium. Aquarium Salt is simply Sodium Chloride, and does not contain minerals and trace elements like calcium and iodine like sea water mixes. Adding small portions of this salt can help to treat osmoregulatory stress, an imbalance or disruption in the exchange of salts and minerals between the fish itself and its environment. Stressful situations such as transport, disease, or injury can cause osmoregulatory stress, but if used properly, aquarium salt can increase blood and oxygen flow through the gills, helping the fish relax and heal. When used in higher concentrations for short time periods as a dip or bath, salt can help to build a the protective slime coat on the body, preventing parasites from attaching and even killing one-celled parasites like Protozoa, that may already be on the fish. While aquarium salt does have some benefits, it is not a necessary additive. Once introduced to the tank, salt does not evaporate out of the tank. It can only be removed with water changes and plants, inverts and other sensitive species may be negatively impacted if the concentration is allowed to rise.

Rift Lake Salts

There are also specialized salt mixes for African Cichlids. These mixes are formulated to help reproduce the water conditions of the Rift Lakes where the fish are native. They extend the same benefits as plain aquarium salt, buy they also contain minerals like magnesium, calcium, sodium, potassium, and other trace components that are found in those unique Rift Lake environments. These elements are essential for the long-term health and well-being of the fish. These mixes also contribute to raising and maintaining hardness and alkalinity.

Artificial Seawater

Now, on to the numerous mixes formulated to create seawater for marine tanks. Sea water is not just “salty”; it contains a precise mix of trace elements, all of which should be present in an artificial replacement. Using a commercial salt mix, you create water for the aquarium that is in many ways superior to natural sea water, with buffers to help maintain the proper pH, as well as additional calcium and other trace elements to maintain corals, clams and other reef invertebrates.

Seawater is composed of many different ions (salts) in different concentrations. The main ions are sodium (Na), chloride (Cl), magnesium (Mg), and sulfate (S04), forming the salts (NaCl and MgS04).  Salinity is the measure of the concentration of dissolved salts (ions) in the water, often given in ppt – parts per thousand.  Normal seawater is about 35 ppt salts. You’ll be looking to maintain a specific gravity reading between 1.019 and 1.025 depending on what is in your tank.

Making saltwater for your aquarium begins with finding a pure water supply. Many aquarists prefer to use RODI units that combine reverse osmosis (RO) and deionization (DI) to remove impurities and undesirable compounds from tap water.

You may need to do a little research when choosing a salt mix, to find what will suit your system best. Not all salt is created equal in the aquarium world. Each brand of marine salt mix varies from natural seawater’s concentrations of the four major ions (sodium, chloride, sulfate and magnesium), as well as other trace elements. Follow the manufacturer’s directions on how much mix to use, and check the solution for proper salinity as you add mix using a hydrometer or a refractometer. Add more salt mix to raise the salinity or more fresh water to lower salinity. Make sure all salt is completely dissolved before testing to ensure accurate readings.  Altering salinity of your tank significantly may also alter alkalinity, calcium, magnesium, and other ions to the point where they will need adjustments, so be sure to have test kits on hand to monitor these levels. Some of these elements may also need to be regularly supplemented, particularly in heavily stocked reef tanks, as the amounts supplied by the salt mix alone will be depleted quickly.

A Note on Brackish Tanks

Seawater salt mixes should also be used if you’re creating or maintaining a brackish water system. Brackish water habitats are created in estuaries where rivers and streams meet oceans and the freshwater and saltwater mix. Sea Salt mixes will supply the necessary elements to your brackish habitat in lower concentrations, mimicking the conditions in their natural habitat.  Brackish aquarium water typically ranges between 1.002 and 1.022 specific gravity, and a 50/50 mix of fresh and mixed marine water should provide water in that range. While most brackish water fish will live happily in this concentration, you should know the conditions of the fish or inverts you’re keeping and adjust as necessary. Some brackish fish start their lives out in freshwater and eventually make their way “down the estuary” to become fully marine fish as adults.