Does Aquarium Salt Kill Beneficial Bacteria? {What You Need To Do}

Do you need to add aquarium salt to your tank? Does aquarium salt kill beneficial bacteria?

Learn how to use aquarium salt in your tank safely. I was in the same position a year ago and couldn’t find a good article to help explain it.

I wrote this article to help you understand the relationship between beneficial bacteria and aquarium salt.

Does Aquarium Salt Kill Beneficial Bacteria?

No. In a freshwater tank, using aquarium salt can have a variety of advantageous effects. It is, at best, a low-cost preventative measure, and it doesn’t affect the healthy bacteria in your tank.

Moderate salinity is tolerated by helpful microorganisms. As a result, treating the tank water with aquarium salt at low quantities won’t cause any harm to the fish.

Higher aquarium salt concentrations, however, have the potential to harm beneficial microorganisms and interfere with the tank’s built-in filtration system.

Is Aquarium Salt Safe for All Fish?

Yes. Using aquarium salts is suitable for all fish. In fact, it leaves a lot of positive effects if you use the suitable salts in an appropriate dosage. At best, it is one of the cheapest preventives and treatment health care for your fish.

Using aquarium salts of the right quality in an appropriate quality offers many benefits to your tank. Some of the advantages of aquarium salts for fish include;

  1. Help you in the control and treatment of various parasites, including flukes and ich.
  2. Improve your fish’s ability to have a protective slime coat that aids speedy recovery from infections and injuries like torn fins.
  3. Mitigates the possible intake of lethal nitrates during the nitrogen cycle in new and existing tanks.
  4. It limits stress by improving the gill function in fish. The osmosis caused by the effect of these salts reduces the amount of water intake by the gills. Consequently, it eases the burden on the kidney.

Ensure that you add an appropriate amount of aquarium salt in the tank, depending on the fish type. Some fish species are more salt-tolerant than others. For instance, smooth-skinned fish like loaches, plecos, and Corydoras are less salt-tolerant compared to Angelfish.

Can Salt Kill Good Bacteria?

No. Beneficial bacteria are found in various parts of the tank, such as :

  • substrates
  • glass walls
  • filters
  • decorations

There is no way these bacteria will not be affected. The only question is if the salts will kill these bacteria or not.

Beneficial bacteria can withstand a moderate level of salt concentration in the tank. So, the organisms will not get hurt or die when you dose your tank with a medium to a low amount of salt. A high concentration of aquarium salt can kill the beneficial bacteria on your tank.

How Does Beneficial Bacteria Help?

Beneficial bacteria enter the tank via various means. They enter as a single entity and grow into multiple colonies if the condition is favorable.

They perform several active and passive roles. Some of the benefits of bacteria in the tank include:

  • balance the nitrogen cycle in your fish tank
  • filter and clean the aquarium
  • break down some toxins in the tank into less harmful substances
  • manage ammonia spikes
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How Often Should You Add Salt to A Freshwater Aquarium?

It is best to add aquarium salts to your tank when there is a crisis like infection or parasite invasion. You can also add it occasionally as a preventive measure in the tank. It will even work better when you combine it with other medications.

Consider starting with only one tablespoon of aquarium salt for 5 gallons of aquarium water. Expert aquarists consider this dosage safe for almost all fish species, plants, and beneficial bacteria.

Watch your aquarium for 24 hours. You can repeat the dosage for four days if there are no changes or improvements. Consider making a water change of up to 25% on the fifth day.

How Does Aquarium Salt Affect Beneficial Bacteria?

Chemicals found in tap water, such as chlorine, are dangerous to aquarium microorganisms. Furthermore, certain drugs have an impact on them. Even household cleaners like bleach or hot water can destroy good bacteria.

  1. Use extreme caution when adding any new element to an aquarium.
  2. A little rise in water salinity is tolerated by the beneficial bacteria in fish tanks.
  3. When used at therapy levels, aquarium salt won’t harm the bacteria.
  4. Aquarium salt can cause problems for good bacteria when concentrations are high.
  5. The bio-filter will become inoperable if the filtering bacteria are killed.
  6. Once a bacterial colony has been destroyed, it is difficult to re-establish it.
  7. Your tank will begin to see ammonia increases if there are no beneficial microorganisms present.

Does Aquarium Salt Change the Levels of Ammonia?

Yes. Add aquarium salt to your tank to lower the ammonia levels. Your tank water may be made more ammonia-free by adding one tablespoon of salt every 10 gallons.

This keeps the fish and other aquarium residents in a healthy environment.

Should I Use Aquarium Salt Regularly?

No. Even though aquarium salt is largely made of natural ingredients, you should only use a small amount of it to cure your fish.

It should only be used if you believe your fish are being stressed out by diseases, parasites, or other microbes.


The majority of aquarium salt producers include the necessary dose. It is best to stay within this range. Depending on what it will be used for, the concentration may change.

As a preventative measure, lower amounts are sufficient. However, you’ll need bigger amounts to treat ailments.

Aquatic plants, fragile fish, beneficial bacteria and filtering microorganisms in the tank will all suffer from high aquarium salt concentrations. Less is more and dose slowly.


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John Brandon

John has kept fish all his life (since he was about 5). He started with keeping guppies and fell in love with fish keeping almost straight away. That was 40 odd years ago. These days John still keeps fish and currently has two large tanks where he keeps many different types of fish such as Angelfish, Neon Tetras, Goldfish, Guppies and many more.