Do I Need To Add Salt to My Freshwater Aquarium?

Most people, unless you have a lot of money, have freshwater aquariums in their homes. Saltwater set-ups and the fish that go in them can be very expensive to start and maintain.

Freshwater is naturally occurring water. It has a low concentration of dissolved solids and salt. It is not from the sea but lakes, rivers, and streams. Freshwater tanks are normally for pet-keeping or decorative purposes. But some people also keep them for research.

Do I need to add salt to my freshwater aquarium? You should never put salt in your freshwater aquarium. It is recommended that if you have sick fish, you should quarantine them in a separate tank, and treat them with salt or other medications. You should also never use salt in an aquarium that has live plants.

Salt can be an effective medication. But this is only if your fish are salt tolerant. Most freshwater fish can tolerate very low levels of salt because the lakes and rivers they come from have very little detectable salt.

Salt will dehydrate (take all the water out of) your live plants and they will die. You want your tank to mimic the fish’s natural habitat as closely as possible. Lakes, rivers, streams, and creeks have a low level of salt, measured in parts per million. Parts per million is a complicated scientific calculation. It can also be described as milligrams per liter (mg/L). 

Today we will discuss when and when not to add salt to your freshwater tank. We are going to give you a clear understanding of why to add salt to your freshwater tank, how much to add, and the side effects.

Remember, this is not recommended! On very rare occasions it may be needed; stress reduction, medicating, adding hardness to the water, and because you have fish that are used to brackish waters.

What Is Aquarium Salt, Exactly?

Add Salt to My Freshwater Aquarium

Aquarium salt is a general term that covers a large variety of salts. Different elements are called ‘salt’. Minerals included in some of the salts are:

  • Ammonium
  • Calcium
  • Magnesium
  • Potassium
  • Sodium

Some compounds are sometimes included. You have 3 common types of aquarium salts that you could use in your freshwater tank. 

  1. Freshwater Aquarium Salt: this is specially designed for freshwater aquariums, while table salt is NOT. There are no additives added and it can easily be found in pet stores or ordered online.  
  1. Non-Iodized Rock Salt: these particular salts are pure sodium chloride. No extra ingredients are added to this type of salt. Because of this, they are very popular in your freshwater aquarium.
  1. Marine Salt: this is a very different kind of salt. It is a lot more complex and is made of different materials. Magnesium and calcium being 2 of them.

Now, some people say you should only add salt to your freshwater aquarium if you have fish that have been poisoned by nitrite or have been affected by parasites or fungal disease.

Then you have other aquarists that swear by keeping an aquarium lightly salted. They feel that this helps to keep your fish healthy and they use it to prevent parasites, fungus, and nitrite poisoning.

How Does Salt Work In An Aquarium?

If you raise the salt content in your aquarium, then water will be removed from fungus, bacteria, and parasites. Salt is a good ‘medicine’ alternative that is effective against the parasites, bacteria, and fungus that can invade your tank.

You need to be extremely careful because fish all have a different tolerance to salt. It is easy to overdose/add too much salt to your tank, which may kill everything along with the bacteria. 

How To Use Aquarium Salt?

Salt comes in many-particle sizes, chemical compositions, and purity levels. When using salt in your aquarium you do not use regular table salt. You need to use salt especially made for aquariums, rock salt, or marine salt. The most recommended is Fritz Freshwater Salt. It is suggested that you use it in a quarantine tank or one without live plants.

1 tablespoon is ideal for 3 gallons of water. You want to start with the lowest level of salt and very gradually increase it. There are 3 levels of treatment when you are dealing with sick fish.

  1. As mentioned above, the first level is going to be adding 1 tablespoon of salt per 3 gallons of water. You can either put it directly into the tank or you can dissolve it in a small cup of water first. This stage is for mild cases of bacterial and fungal infections. 
  1. This is going to consist of 1 tablespoon of salt per 2 gallons of water. This level of treatment should take care of Ich (also known as white spot disease) within 10 days. 
  1. 1 tablespoon of salt per 1 gallon of water. This level of treatment should knock out anything that is going on in your aquarium. But it is also hard on sensitive species of fish and scaleless fish. It is recommended that you do extensive research before doing this level of treatment.

You have to keep in mind that the aquarium salt will not evaporate or be filtered out of the water. You will need to do almost a complete water change to get rid of the salt in the aquarium. 

The optimum situation for the use of salt is when there have been nitrite poisoning and/or parasites. If you are treating external parasites a ‘dip’ is highly recommended. To do the dip you need a clean bucket, 4 teaspoons of salt, and a gallon of water. The salt needs to be completely dissolved before adding your fish to the bucket. Once the fish are added, leave them in the bucket for 5 to 30 minutes. 

Should Salt Be Used As A Routine Tonic?

According to 2 different fish veterinarians, you should not use salt as a routine in your freshwater aquarium. The only time you should do so is if your fish are used to brackish water. Freshwater fish should only be kept in freshwater. 

No one knows the actual effect that salt can have on a fish. Does it burn their eyes? Does it bother their gills? If you put a freshwater fish in seawater or a saltwater set-up, sooner or later they will die. We do not know if there are any long term effects of salt on freshwater fish.

If you have a fish species that has a natural requirement for salt then that is one thing. Otherwise, you should never add it to an aquarium as a routing, nor should you add it to a pond. Salt may be used as a supportive mechanism for salt-tolerant fish who have ulcers or a major skin breach.


The most important thing to say here is to do extensive research before you use salt in your freshwater tank, for any reason. You could have fish that are going to be highly sensitive to the salt and if you accidentally overdose then they are going to pass on.

If you have many different species of fish in your freshwater aquarium it will be easier to get a ‘quarantine tank’ and move the ill fish before performing a salt treatment. This saves the fish that are not sick from having any ill effects from the salt treatment. 

You can also do a salt dip specifically for the sick fish. This includes 1 gallon of water, 4 teaspoons of salt, and a clean bucket. Dissolve the salt before adding the fish and then allow them to soak/swim for 5-30 minutes.

If you do end up adding salt to your freshwater tank you will have to do a complete water change to remove all the salt once the fish are healed. The salt doesn’t evaporate and it isn’t removed by the filtration system. 

It is NOT recommended that you add salt to a freshwater tank, other than to treat sick fish (parasites, bacteria, fungus, or nitrite poisoning). Unless you have fish that are used to living in brackish water, there is no need for the salt in a freshwater tank as a routine occurrence. 


I'm passionate about fish pets and love sharing everything I learn about them.

Recent Posts