Contrary to popular belief, adding salt to your freshwater aquarium is like using a double-edged sword. On one side there are the benefits that range from assisted healing, to the formation of slime coating, improved gill function, parasite control, and inhibiting nitrate uptake. On the other side, there are many fish and plants that cannot tolerate salinity in their water, and adding salt may harm if not kill them.

Before you add salt to your freshwater aquarium, you should make sure that it is iodine and additive free. Also consider how you intend to use it, and how to avoid any possible side effects.

Why Do Hobbyists Use Salt

Some pet store clerks may advise you to add 1 teaspoon for every 10 gallons of water. The belief is that this can help with building hardiness in your fish, reduce stress, fight off nitrite poisoning, and to assist the fish with osmoregulation by helping the fish maintain the sodium levels in it’s blood.

Other hobbyists will only use salt to make the water harder and to maintain it’s salinity to create brackish water conditions. These hobbyists may only consider using salt to medicate their fish when treating several conditions.

Enthusiast may also limit the use of salt, for recharging their zoelite rocks. When exposed to fresh water, zeolite can remove ammonium/ammonia from the aquarium. By soaking the zoelite in salt water, it exchanges the ammonium/ammonia with sodium, which can later be removed with fresh water.



When Not to Use Salt

Even for treatment purposes, there are times when salt should not be used or at the least avoided altogether.

Live Plants

If your aquarium has plants as part of its decor, it is advised to not put salt into your tank. Most freshwater plants can be damaged by salt, even at relatively low dosage levels. Here are some plants that can be more hardy and may tolerate salt bath treatments:

  • Anacharis (Egeria densa)
  • Anubias (Anubias barteri)
  • Java Fern (Microsorum pteropus)
  • Java Moss (Taxiphyllum barbieri)
  • Moneywort (Bacopa monnieri)

Soft Water and Scaleless Fish

Fish that can not handle hard or salty water, can be harmed even by low levels of salinity. Scaleless fish such as Cat Fish (Corydoras) can have the skin damaged, as the salt content can dry out the protective film that coats their body. If you need to give your aquarium a salt bath, leave these fish in a separate tank until the main tank has had a near 100% water change following the treatment. Here are some alternatives for treating these sorts of fish:

Do Not Add More Salt During Treatment

If you are using a salt bath to treat your aquarium. Do not top up the tank with more salt water solution. Salt does not evaporate and can only be removed with water changes. When using that bath treatment, perform weekly 25% water changes. Repeat this process for up to 3 weeks, or until the symptoms are gone. To ensure that as much of the salt has been removed as possible, you will need to perform a near 100% water change at the end of the treatment.

A Hospital/Quarantine Tank

If you have a sick or injured fish(s), you can isolate them in separate tank while they recover.  If your fish has damaged skin or lost a lot of scales. The sodium in the water can help with osmoregulation and encourage the repair and growth of new skin and scales. It can also help to reduce stress while your fish is in recovery.

Setting Up Your Hospital/Quarantine Tank

By using 1 teaspoon of salt for every 10 gallons of water. We are able to create a solution that can aid in the healing process. Some fish like Mollies and Central American Cichlids may be able to handle much more sodium. Follow the instructions on the packet and do your research on how much salt content your fish can handle. Generally a tropical rain-forest based fish, will not be able to handle as much sodium as a fish that can live in brackish water.

  • 1/3 of the isolation tank needs to be filled with water from the main tank
  • Relocated the patient(s)
  • Slowly fill the remaining 2/3 with freshwater
  • Fill a container with some of this water and add the appropriate amount of salt based on the tanks size
  • Stir this solution until the salt has fully dissolve and slowly pour it into the tank
  • Keep an eye on your fish and watch for signs of stress.
  • If the fish are showing signs of stress remove them from the tank immediately
  • Repeat the process and with less salt until the fish are able to comfortably handle the salinity levels
  • Every week for the next three weeks. Perform water changes at 25%
  • Return your fish to the main tank once it has recovered

Giving Your Tank a Salt Bath

A bath is ideal for treating the entire tank for stress, nitrite poisoning, and for some parasites. By using a salt concentration of up to 1%, we are able to provide the same sort of benefits as the quarantine isolation tanks.

  • Make sure to remove any salt sensitive fish and plants from the tank prior to treatment
  • Set aside some tank water just in case the fish do not take to the treatment and need to be removed
  • Measure out the appropriate amount of salt that is needed for both your fish and the size of your tank
  • Observer your fish and watch for signs of stress.
  • If they are not taking to the salinity solution, remove them immediately and start again with less salt
  • When your fish are comfortable with the solution leave them to recover
  • Perform weekly water changes of 25% for the next 3 weeks
  • If you need to reintroduce salt sensitive fish and plants. Make sure to perform a near 100% water change prior to their reintroduction

Saltwater Dips

We must stress that while using saltwater to treat external parasites can be effective. It can be very stressful and if done incorrectly, very harmful for your fish. As it needs to be done with higher salinity concentrations. If you do not feel comfortable using aquarium salt to treat parasites. There are safer medications like the ones mentioned above, and can be bought from your local supplier or online.

Steps For Saltwater Dips

Saltwater dips need to use a lot of salt, about 1.5 cups of salt for every 10 gallons in fact. Not every freshwater fish can handle this level of salinity. Some fish will straight up reject this solution and may try to jump out the moment they are placed inside of it. Other fish will only be able to stay inside the solution for a short period of time of up to 30 minutes. While the rest may last up to 2 hours before they need to be removed.

  • Take the required amount of water from the main tank
  • Using a small quantity of water in a separate container, dissolve the appropriate amount of salt
  • Slowly add the solution to the water
  • Have fresh water set aside for when it will be needed
  • Introduce your fish to the solution and constantly monitor them
  • Remove your fish and return them to freshwater immediately if they are presenting signs of excessive stress
  • Keep your fish in the solution for no longer then 2 hours
  • Isolate your fish following treatment and observe for parasite activity
  • If the fish is comfortable with the solution’s level of salinity you can repeat the process if necessary
  • If the experience was stressful for the fish, it is advised to not repeat the process and to seek other treatments

Parasite That Can Be Treated with Saltwater Dips


Here is a list of ectoparasites that can be treated using the saltwater dip. Some parasites are more receptive to this sort of treatment, while others may require multiple treatments.

  • Ich (Ichthyophthirius)
  • Costia (Ichthyobodo)
  • Anchorworms (Lernaea)
  • Gyrodactylus (Skin Flukes)

See our article for more information on Disease and Treatments.


Unless you are comfortable with mixing solutions and fully understand the tolerances of your fish and plants. It would be best to advise you to use other medical treatments when treating your fish for illnesses and parasites. Aquarium salt is best used for creating brackish water conditions, or by experienced enthusiasts for treating their fish.

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