Salt therapy is one of the most common ways to treat a wide variety of illnesses in freshwater tropical fish like guppies. Unfortunately, it’s not always done correctly. If salt is used in some circumstances, it can actually cause more harm to your guppies. Here’s what you should know about salt treatment for fish disease.
Which Type of Salt?
The first thing to understand is there are two types of salt you may see, but they have very different applications. Freshwater aquarium salt — also called livebearer salt or tonic salt — usually has some mineral salts to buffer pH changes in the tank. The usual dosage is one or more teaspoons of freshwater aquarium salt per gallon.
Marine aquarium salt, on the other hand, is meant to produce artificial seawater with a heavy mineral composition that helps resist changes in pH.
Note: aquarium salt is very different than the table salt that you put on food. Table salt contains traces of calcium silicate and iodine, which are not found in aquarium salt.
Why Does Salt Help?
It’s not so much the salt that helps fish but the change in salinity in the water. The theory is that bacteria and other pathogens have little ability to compensate for changes in salt concentration in the water, whereas fish have internal organs that allow them to adjust to small changes. Changing the concentration of the salt in the water weakens pathogens without hurting the guppies, allowing the fish to fight back against weakened pathogens. This is the same reason sick marine fish are often treated with a freshwater bath.
Avoid Salt for Fin Rot and Fungal Infections
Salt usually won’t help treat external bacterial infections in guppies, including fin rot. The better option is using antibiotics and antibacterial medications.
Do You Have a Brackish Aquarium?
Some guppy owners keep them in brackish water. If you have a brackish aquarium, don’t use freshwater aquarium salt for a treatment. Instead, use marine aquarium salt.
How to Make a Salt Bath for Sick Guppies
Guppies suffering from ich and other pathogens may benefit from a salt bath. Start by adding one tablespoon of salt to a gallon of water that’s at the same temperature as your aquarium. Place your sick guppies in the bucket of salted water for five minutes, removing them early if they show signs of stress. After five minutes, add two cups of tank water to the bucket then wait ten minutes before adding another two cups. Repeat for thirty minutes then put your guppies back in the tank. Do not reuse the water in the bucket.