Epsom Salt Bath Guide for Aquarium Fish

Carol M.
Fisheries Consultant

Epsom salt refers to a compound containing magnesium, sulfur, and oxygen. The salt carries the name Epsom, a town in England where it was discovered. Magnesium is beneficial to human bodies, especially the nerves and muscles. You shouldn't confuse this salt with common table salt as the two are different, and Epsom lacks sodium.

When you use the Epsom correctly in your fish, it acts as a laxative and reduces swelling. Thus, it reduces swelling in dropsy, popeyed, wound infection, and swim bladder disorder. This salt helps a bloated fish expel air, feel well, swim, and sink better. 

You can still use this salt to regulate water hardness in saltwater tanks. Increasing water hardness applies in marine aquariums with stony corals. So, let’s find out how to use Epsom salt bath for your fish.

Uses of Epsom Salt

This salt has excellent benefits to your fish, but it doesn't treat any pathogenic disease. Some of its uses include:

  • Treats Swim Bladder Disorder

Your fish may be having trouble swimming well. They may be swimming upside down or stuck at the bottom or top of the tank, or having a swim bladder disorder. Swim bladder disease may result from many factors like pathogenic where Epsom salt can't help. But, if the condition is from overfeeding, Epsom salt will treat the buoyancy issue using a salt bath. It's best to avoid feeding the fish for around 24-48 hours before a salt bath.

swim bladder disease
  • Treats Constipation

The salt helps your fish relax muscles and make them poop. The treatment should be one tablespoon of salt per gallon of water in a quarantine tank.

  • Helps in Dropsy Treatment

This salt helps draw fluids out of a fish's body. Though several factors cause the infection, some are treatable. By use of Epsom salt along with other medications, you increase the chances of survival for your fish. The salt will release any swelling in the abdominal regions and help your fish return to a standard shape.

  • Adjust Water Hardness

The salt helps increase magnesium ion concentration, especially in marine aquariums. Some fish require more hard-water than others. Hard water also influences the water pH, where hard water is alkaline and soft water acidic. Therefore, you can use Epsom salt to regulate water hardness and raise the pH. However, you may need to monitor the pH to avoid changes greater than 0.3 in 24 hours.

How to Do an Epsom Salt Bath

The preparation of an Epsom salt bath involves the following steps and materials.

What You Require

  1. Quarantine tank
  2. Reviving tank
  3. Thermometer- for checking water temperatures in both tanks. Check this out:
  1. Stopwatch/ Phone timer- to set the time needed for treatment
  2. Measuring spoon – to help measure the proper amount of the salt
  3. Net – for safely transferring the fish in the tanks
  4. Epsom salt- consider buying this salt:

So, Let's talk about the steps you have to follow

  1. Pour a gallon of water from your fish tank into a quarantine. You want to use the water tank to ensure it has favorable temperatures for the fish. You can confirm the temperatures with a thermometer.
  2. Prepare a second container (reviving tank). It should have a quarter of treated salt bath and ¾ of aquarium water.
  3. Add a one-flat tablespoon of Epsom salt into the quarantine tank and mix it until it dissolves.
  4. Pick your fish from the tank and place it in the saltwater bath using a net. Leave the fish in the bath for 5-10 minutes. This time will vary for various species, so it's best to observe how your fish responds and take it out if stressed. If the fish gills stop moving or the fish loses balance, it’s passing out, and you should remove it immediately and place it in the revival tank.
  5. Watch your fish closely and note how it responds. Remember, larger fish may be more tolerant than young ones, so you need to adjust the time accordingly. If the fish seems stressed in a few minutes and swims weirdly, remove it and use a lower salt concentration next time.
  6. The time limit depends on your fish species and the condition it has. So, after time elapses, transfer your fish to a revival tank. This step helps reduce stress and potential shock.
  7. After five minutes, carefully remove your fish and return it to the home tank. You may consider observing your fish for a few minutes to ensure there are no complications from the treatment.


Epsom salt is of excellent use to your fish, especially for internal physical issues. The salt helps treat the infections caused by physical factors and is not pathogenic. For instance, it helps your fish poop out internal parasites, relieve bloating, and reduce swelling. Before making a salt bath, you should consider your fish condition, the species and use the appropriate amount of salt.  Remember,  to monitor your fish behavior in the salt bath, and if it shows any sign of stress remove it immediately.

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