Many freshwater aquarists use or at least have heard of using salt in their freshwater aquariums, but few seem to know why. Most “read about it somewhere”, “heard it from someone”, or “saw it on the shelf so I must need it”. To some, it may be beneficial but to others it can cause far more harm than good.
What exactly is Aquarium Salt?
“Salt” is a very broad chemical term and can refer to an unlimited combination of elements. The salt used in freshwater aquariums is Sodium chloride (NaCl). This is NOT the same thing as what is probably in your kitchen and is NOT the same thing that saltwater aquarists use for their corals and clownfish. The “table salt” used as a condiment is mostly NaCl, true, but most table salt is Iodized Table Salt and contains iodine, de-caking agents, and possibly potassium or other trace elements. The marine salt used in saltwater aquariums is mostly NaCl, also true, but has buffers and other elements like sulfate, magnesium, calcium, potassium and others. All of these extra ingredients can range from unnecessary for to harmful to freshwater aquariums, affecting the biology of freshwater plants and animals directly as well as changing the water chemistry in the tank. For freshwater aquariums, use only salt sold as freshwater Aquarium Salt or pure NaCl like Kosher Salt or Rock Salt.
Why do you need it?
Aquarium Salt as discussed here is NOT used to make your tank a saltwater or brackish aquarium. Aquarium Salt is used as an additive to add electrolytes to the water, as a stress reducer and as parasite prevention. All of these sound like good reasons to add salt but as with other additives and medications, it is important to know what you are treating and why before settling on a “magic bullet”. The stress that Aquarium Salt can help treat is osmoregulatory stress. This happens when the salts and minerals inside the body of the fish get distorted and out of balance for some reason (transport, disease, injury, etc.). Adding salt to the water changes the ratio of salt between the fish and the water and how the fish reacts to it. Used properly, this can increase blood flow in the fish (since the NaCl ions are carried in the fish’s bloodstream) which can improve oxygen flow and helps the fish relax or heal. Aquarium salt as parasite prevention is most effective as a dip or bath (higher concentrations for limited time periods) rather than a constant treatment in the aquarium. Since fish have more advanced osmoregulation (that word again – how they can balance salts in their body) than one-celled parasites like Protozoa, they can survive salt concentrations that parasites cannot. This can be a gentler, more holistic approach than some harsher medications for minor parasitic outbreaks on otherwise healthy fish.
How is it used?
The concentrations recommended for Aquarium Salt use can vary. As a dip, you can use around a 3% solution (this translated to around 7.5 tablespoons per gallon) for anywhere from 5 minutes to half an hour, depending how well the fish are reacting. If a fish starts showing extreme signs of stress like very rapid breathing or rolling over onto its back or side, take it out and get it back into freshwater right away! A bath is a more extended dip and involved higher-than-normal concentrations in the main aquarium or a hospital tank. Concentrations for a bath are usually recommended around 0.5-3 teaspoons per gallon and the salt is not replaced after water changes. Some livebearers (platies, guppies, swordtails, and mollies) do well with some extra salts and electrolytes in the water. For these fish, replace the salt in the new water during water changes. For example, if a 10 gallon tank has been treated with 3 teaspoons per gallon and you do a 1 gallon water change, add another 3 teaspoons to the new gallon of water that you add back into the aquarium. Salt does not evaporate and is only removed from an aquarium through water changes.
Whenever adding salt make sure it is already dissolved before adding it to the aquarium. Dissolve it completely in a small container of water and them dump that salted water into the main aquarium. Undissolved salt can burn fish and cause internal problem if they attempt to eat any grains of salt that they might think are food. Also, plants and some fish (scaleless fish like some catfish, tetras like Neon or Cardinal Tetras) are very sensitive to salt levels. Do not use Aquarium Salt in planted aquarium and use extreme caution with sensitive fish.
The Moral of the Story
Salt is an additive and salt is a medication. Just like any other additives and medications, it is a good idea to know what you are adding, why you are adding it, and what is will be doing to your fish and aquarium. Just like many other products and treatments in our hobby, Aquarium Salt has its Pro’s and Con’s and you’ll find aquarists who swear by it and those who swear against it. You have to look at it for your own situation and decide what is best for you (or give us a call or message and we’ll help you figure it out!).