Guide to Aquarium Salts


If you own a freshwater aquarium, you may be surprised that aquarium salt can be beneficial to your aquarium. In fact, it is imperative you understand the importance of aquarium salt and when to use it in your freshwater aquarium. This is something that all fish owners should understand.

Aquarium salts can offer a wide range of different benefits for the health of your fish. In order to keep your freshwater fish happy and healthy, providing them with aquarium salts when necessary is an integral part of their management and care. Unfortunately, many fish owners are not aware of what aquarium salt is or how to properly use it.

Read on to learn more and find out why freshwater fish need aquarium salts for their health and vitality.

Aquarium Salt

What is Aquarium Salt and What is it Used For?

Aquarium salt is a type of salt that is used in the aquarium hobby in order to promote the health of the fish.
Aquarium salt is used to prevent disease and other health issues. It can be added to the aquarium water in low dosages regularly in order to maintain the health of the fish. Essential electrolytes can be lost during water changes. Therefore, adding low dosages during regular water changes may be beneficial for some fish.

Aquarium salt can also be added in higher dosages temporarily in order to treat a health issue the fish may be experiencing. Compared to many other supplements and medication for fish on the market, aquarium salt is much more affordable. When used properly, aquarium salt can be very useful in fishkeeping.

Keep in mind that overdosing salt in a freshwater aquarium can be harmful. In addition, different fish has different salinity tolerance. For example, livebearers such as guppies and mollies has a higher salinity tolerance than most other fish. Other fish, such as scale-less fish, are known to have very low salinity tolerance. This includes many species of catfish. In addition, when adding salt to an aquarium, keep in mind that aquatic plants and other invertebrates that may be living in the aquarium may suffer. Therefore, it is important to understand each species’ salinity tolerance before adding it to an aquarium. Understanding this will allow you to make sure that your fish and the entire aquarium is healthy.

Aquarium Salt Benefits

Aquarium salt can offer a number of different benefits.

One benefit to aquarium salt is that it adds electrolytes to the freshwater. This helps improve the gill function of the fish, allowing them to breathe properly. A lack of electrolytes may cause serious health problems for these fish.

Another benefit to aquarium salt is that it can be an anti-pathogenic substance. Aquarium salt causes pathogens such as bacteria and fungi to die due to dehydration as a result of the increased water salinity. This helps prevent your fish from getting attacked by these harmful pathogens.

While high salinity levels can be harmful to the fish, the pathogens will most likely be affected by the salt before the fish. This is due to the substantial difference in mass to surface area ratio. Therefore, the pathogens will dehydrate and die, before the fish are significantly affected. This is the reason why salt treatments are effective.

If you use the right amount of aquarium salt, your fish will be unaffected by the slightly different water salinity and will be healthier for it as a result. Using aquarium salt is a cost effective and sparing method that can be used to improve the health of your fish.

Aquarium Salt for Fin Rot

If your fish have been suffering from fin rot then aquarium salt could be a good option. Fin rot causes the tail of the fish or its fins to appear frayed. This can be caused by either bacterial or fungal infections. Fortunately, an appropriate level of aquarium salt can help to prevent both of these pathogens.

Aquarium Salt for Ich

Ich is a condition that is very common in freshwater fish, and aquarium salt can help treat this parasite. Symptoms of ich are visible as white spots on the fishes’ scales. In addition, fish that are suffering from ich may show other symptoms. For example, they may try to scratch its body on hard surfaces such as the aquarium substrate and décor.

In order to treat ich with aquarium salt, use a tablespoon of salt for every 1-3 gallons of water. Start with the lowest concentration of salt, and gradually increase the concentration as needed. This should cure the fish in approximately 2 weeks. Severe cases of ich can take longer to cure. The reason why ich can take a long time to cure is because it may not eliminate all of the ich parasite at once. The effectiveness of the aquarium salt can vary depending on the stage of the lifecycle that the parasite is in. As tomites, the parasite is freely floating in the water. This is when they are most vulnerable to the aquarium salt. By increasing the water temperature, you can speed up the lifecycle of the parasite and help the fish recover faster. It may be beneficial to raise the water temperature above 86°F, if your fish can handle it.

Aquarium Salt Substitutes

If you do not have aquarium salt at hand, you may have considered using other types of salt as substitutes. Not all types of salt are suitable for your fish, but there are suitable substitutes to aquarium salt.

Is Aquarium Salt and Table Salt the Same?

Aquarium salt and table salt are not the same. However, there are some types of table salt that can be used as a substitute to aquarium salt.

Table salt that you use for aquarium fish must be non-iodized. While fish do need iodine, they get enough of it from their fish food. Giving more of it through salt will most likely do more harm than good.
Table salt should not include additives such as anti-caking compounds. This can be dangerous to your fish.

Table salt that are non-iodized and does not includes additives may be used for aquarium fish. Be sure to read all labels and use caution.

Aquarium Salt vs Sea Salt

Aquarium salt and sea salt is different.

Aquarium salt is sodium chloride, or NaCL. It does not contain other trace mineral or elements. For freshwater aquariums, aquarium salt should be used.

Sea salt, or marine salt, contains trace minerals and elements. The exact amount of trace minerals and elements will vary by the manufacturer. Sea salt is often sold under the brand name Instant Ocean. Essentially, they are evaporated ocean water. They are used for saltwater aquariums.

While your freshwater fish may benefit from aquarium salt, they may not benefit from all of the trace minerals and elements in the sea salt. In addition, be aware that sea salt can affect the pH of the water drastically. Therefore, aquarium salt should be used for most freshwater fish.

Other Types of Salt You Can Use as Substitutes

There are substitutes to aquarium salt. Rock salt and kosher salts are common alternatives to aquarium salt. Both of these are made from pure sodium chloride and don’t have any extra chemical compounds added to them. However, when using product that are not intended for aquarium use, be sure to read all labels and use extra caution.

How Much Aquarium Salt per Gallon of Water?

Aquarium salt can be used in different concentration of up to 1 tablespoon of aquarium salt for every 1 gallon of water. However, keep in mind that 1 tablespoon of salt per gallon of water is a very high concentration of salt for freshwater fish. If a fish is coming from an environment with no salt in the water, be sure to acclimate the fish gradually. Start with a concentration that is less than or equal to 1 tablespoon of salt per 3 gallons of water. Once acclimated to a small amount of salt, gradually increase the salt concentration on a weekly basis.

Disease Prevention and Regular Use

For disease prevention, add 1 rounded tablespoon of aquarium salt for every 5 gallon of water. This is dosage could be used for most freshwater fish without irritating them.

Disease Treatment: First Dosage

When using aquarium salt to treat a disease, start the treatment with the low dosage, which is 1 tablespoon of salt for every 3 gallon of water. This is considered a low concentration of salt. Therefore, most freshwater fish will be able to handle this level of salt, with a few exceptions such as some catfish species. If the symptoms do not improve within a week, consider increasing the salt dosage.

Disease Treatment: Second Dosage

If the symptoms do not improve with the first dosage, increase the salt concentration to 1 tablespoon of aquarium salt for every 2 gallon of water. At this concentration, many disease such as ich should be treated effectively. However, if the symptoms do not improve within a week, consider increasing the salt dosage.

Disease Treatment: Third Dosage

If the symptoms do not improve with the second dosage, increase the salt concentration to 1 tablespoon of aquarium salt for every 1 gallon of water. At this concentration, a wide range of issues related to bacteria, fungus, and external parasites will be treated. However, this is a lot of salt for a freshwater fish. While the treatment may be more effective at this concentration, some fish may have a difficult time acclimating to it. For example, some species of catfish and other scale-less fish may not be able to handle this level of salt. Fish species that are generally more tolerant of salt include danios, tetras, silver dollars, and livebearers.

During a salt treatment keep a close eye on the fish. Observation is key. Leave the salt in the aquarium until the fish improves. Once the fish recovers, remove the salt from the aquarium by doing gradual water changes of up to 30% per week. There is a chance that the disease returns when the salt is removed. If the disease returns, gradually increase the salt level back to the appropriate level.

How Much Aquarium Salt for Brackish Water?

Some fish live in brackish water, which are neither freshwater nor saltwater. These hybrid brackish water environments occur in estuaries. Estuaries are where freshwater rivers meet the salty sea.

In order to create a brackish water, you must add the right amount of salt to recreate an environment that simulates an estuary. Refer to the list below for the specific gravity of brackish water in comparison to freshwater and saltwater environments:

Salinity Level of Aquatic Environments

  • Specific Gravity of Freshwater: 1.000
  • Specific Gravity of Brackish Water: 1.005 – 1.012
  • Specific Gravity of the Ocean: 1.025

Add 1-2 tablespoon of salt per gallon of water to recreate a brackish water environment. A hydrometer should be used to measure the actual salt concentration.

Keep in mind that aquarium salt is suitable for freshwater fish. However, in order to recreate a true brackish water environment, you must use marine salt.

Fish Laboratory

With decades of collective fishkeeping experience, we are happy to share the fish care tips that we've picked up along the way. Our goal at Fish Laboratory is to keep publishing accurate content to help fishkeepers keep their fish and aquarium healthy.

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