Should aquarium salt be used in freshwater tanks? Some say it should be dosed all the time to give fish the electrolytes they need, while others say it’s mostly used to treat illnesses. After years of testing with hundreds of fish, we’ve witnessed the true power of salt. As a “medicine” that can kill bacteria, fungus, and external parasites, sodium chloride (NaCl) is one of the best ones on the market. We love it because it’s cheap, easy to get in every country, never goes bad, and can be used in small or large amounts.
But we usually tell beginners to start with our three medicines because different types of fish can handle different amounts of salt, and it can be tricky to figure out and remember the right dose for each species. Another disadvantage is that salt cannot be used with most live plants and snails. Lastly, it’s easy to add too much salt to your freshwater aquarium by accident, which could kill everything in it, not just the bacteria. Still, both new and experienced fish keepers can benefit from this very effective cure as long as they use it correctly and in the right amounts.
Aquarium salt, also known as sodium chloride (NaCl), is commonly used by freshwater fishkeepers to treat diseases and parasites. When used correctly, aquarium salt can be an effective remedy. However, too much salt can definitely be deadly for fish. Understanding proper salt dosing along with your fish’s tolerance levels is crucial.
How Aquarium Salt Works
Aquarium salt makes the water more saline, causing fluids to be drawn out of parasites and pathogens via osmosis. This dehydrates and kills them. Fish are harmed much less because they have more tissue mass and stored water in their bodies. With accurate gradual dosing the salt can eliminate illnesses before harming the fish.
Salt Treatment Levels
There are three main levels of aquarium salt treatment:
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Level 1 1 tbsp per 3 gallons of water. Very mild concentration that’s safe for most fish Used for mild bacterial infections
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Level 2 1 tbsp per 2 gallons of water. For moderate illnesses like ich
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Level 3: 1 tbsp per 1 gallon of water. Highest concentration, used as a last resort against stubborn diseases. Very harsh on sensitive fish.
Dangers of Too Much Salt
While salt can be an effective cure, too high a dosage has risks:
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Osmotic shock – Drastic salinity changes cause fluid shifts that can shock the fish’s system.
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Dehydration – Excessive salt pulls fluid from the fish’s tissues, causing cell shrinkage and organ damage.
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Toxicity – High sodium levels overwork the kidneys and liver. Salt overdoses have been compared to alcohol poisoning.
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Suffocation – Salt may burn gill tissues, making it hard for fish to breathe.
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Immune suppression – Extended high salt concentrations weaken the immune system, leaving fish vulnerable to pathogens.
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Food poisoning – Salt can kill beneficial gut bacteria needed to digest food properly.
Key Signs of Salt Overdose
Watch for these symptoms if you suspect salt poisoning:
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Lethargy and loss of equilibrium
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Labored breathing
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Bloated abdomen or pineconing scales
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Reddened or hemorrhaging fins
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Cloudy eyes
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Weight loss despite eating
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White feces
Fish Tolerance Levels
All fish can tolerate salt to some degree, but levels vary:
Sensitive
- Discus, elephantnose, stingrays, pufferfish, scaleless fish
Moderately Sensitive
- Tetras, rasboras, hatchetfish, freshwater shrimp, snails
Tolerant
- Guppies, mollies, platies, swordtails, catfish, rainbowfish
Very Tolerant
- Livebearers, danios, glassfish, monos, scats, archerfish
Exceptionally Tolerant
- Tilapia, shark catfish, brackish fish like mollies
Best Practices
Follow these tips to use aquarium salt safely:
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Research your fish’s salt tolerance before dosing.
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Increase salt slowly over days, not all at once.
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Remove carbon from filters during treatment.
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Monitor ammonia levels which may spike from dying pathogens.
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Match salt dosages to tank size precisely.
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Only redose salt with water changes, don’t add more.
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Don’t treat sensitive fish like discus at high levels.
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Quarantine sick fish whenever possible.
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Stop treatment if fish show signs of salt poisoning.
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Remove salt gradually over weeks when treatment ends.
Alternatives to High Salt
For fish that don’t tolerate salt well, alternatives include:
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Methylene blue – General antifungal and antibacterial
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Pimafix – Antifungal med derived from tree oils
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Paraguard – Mild antiseptic for external issues
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PraziPro – Treatment for worms and internal parasites
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Kanaplex – Strong antibiotic for difficult bacterial infections
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Furan-2 – For aggressive fungal & bacterial problems
When Salt is Beneficial
While salt should be used judiciously, it does have proven benefits when utilized properly:
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Inexpensive, available worldwide
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Never expires or breaks down over time
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Works against a broad range of pathogens
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Higher concentrations have potency rivaling strong meds
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Can be used indefinitely at lower levels with tolerant fish
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Gentle on biological filtration unlike antibiotics
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Safe for fish when appropriate dose is matched to species
Aquarium salt is a handy tool that can effectively cure many fish diseases when used at the appropriate levels. However, too much salt can certainly be fatal. Know your fish’s tolerance, increase salt gradually, and monitor for signs of toxicity. With some care and common sense, salt can be used to safely treat aquarium fish.
How Long Should the Salt Treatment Last?
Keep the salt in the aquarium until the fish look healthy. Then, change the water to get rid of the salt.
- Do a 100% water change without adding any salt at the end of treatment and then watch for a week.
- If the disease doesn’t come back, change the water again without adding salt and wait another week.
- In the event that the illness comes back, lower the dose of salt and add a little more salt to make the solution stronger. It’s likely that the original salt concentration wasn’t strong enough to completely get rid of the sickness, or the fish didn’t stay in the salt solution long enough to dry out all the pathogens.
How to Use Salt as a Medication
There are different types of salt with different particle sizes, levels of purity, and chemical makeups. For this article, we will only use normal aquarium salt or NaCl rock salt, not table salt, marine salt, or Epsom salt. (Also, the measurement listed below refer to United States (US) customary units, not the UK imperial system. Our treatment starts with the least amount of salt possible and slowly increases it if the symptoms don’t go away.
As you follow our treatment plan, make sure you use aquarium salt. Salt comes in many shapes and sizes.
1 Tbsp Salt per 3 Gallons of Water
Add 1 tablespoon (Tbsp) of salt per 3 gallons of water. You can put the salt right into the aquarium or hospital tank, but some people like to mix it with a little water first. In other words, this amount of salt is not very strong, like putting Neosporin on a small cut. It’s used to fight mild cases of bacterial and fungal infection. It also slightly irritates the fish’s slime coat, which makes it make more helpful mucus that can stop some parasites and microorganisms from getting into its body.
At our fish store, we’ve kept and sold thousands of fish. This salt level is safe for almost all fish, but not for anchor catfish. Leave the fish in the salt water for four to five days. If things don’t get better, raise the concentration.
1 Tbsp Salt per 2 Gallons of Water
For the next level of treatment, mix 1 tablespoon of salt with 2 gallons of water. Level 2 treatment is capable of combating a wider range of illnesses. This recipe can be used for 10 days to treat ich, which is a common illness also called white spot disease. However, if the symptoms are only getting worse after 5 days, try increasing the concentration again.
1 Tbsp Salt per 1 Gallon of Water
When medications and the lower salt levels have no effect, it’s time to bring out the big guns. If you increase the amount of salt to 1 tablespoon per gallon of water, this strong solution will kill almost everything. Level 3 treatment is very harsh on fish without scales and other sensitive species, so please learn more about it first. We’ve seen that rasboras, danios, tetras, silver dollars, livebearers, and most cichlids (as well as their fry) can handle a fair amount of salt. There isn’t much we don’t know about the Caridina crystal shrimp yet, but Neocaridina cherry shrimp can handle salt pretty well.
Note: aquarium salt does not evaporate or get filtered out. As water evaporates, the salt is left behind. Therefore, only add salt (in the proportionate amount) when doing water changes. To treat 100 gallons of level 2 water for ich, for example, you need 50 tablespoons of salt to start. Then, if you need to change the water (or take out 2020 gallons of water), add back 2020% of the salt (or 2010% of the tablespoon of salt) to the new water to keep the same concentration. It’s easy to take too much salt, so be careful when measuring it. Also, unlike most medicines, salt doesn’t break down over time.
If you take out the water that the salt is dissolved in, the salt will not evaporate or disappear. Be careful not to overdose your aquarium with salt.
Do You Need Salt In Your Aquarium? Pros and Cons
Can too much salt kill fish?
If you’ve ever wondered if too much aquarium salt can kill fish, the answer is yes. While a small amount of salt is necessary for a healthy fish tank, too much salt can be harmful and even fatal to your fish. When adding salt to your aquarium, it’s important to follow the directions on the package and not add more than the recommended amount.
Does salt kill you?
No, salt will not directly kill you. However, if you consume foods that contain large amounts of salt over a long period of time, you may increase your risk for developing hypertension, heart disease, diabetes and cancers. Consume a well-balanced diet with a variety of foods such as fruits, vegetables, nuts, seeds, legumes, lean meat and dairy. This will provide the nutrients that are necessary for complete body function and reduced risk for developing salt related chronic diseases.
Is aquarium salt bad for fish?
While aquarium salt can be beneficial for fish in certain situations, it can also have negative effects if not used properly. One of the main concerns is the impact on freshwater aquariums, as salt can make the water brackish and harm freshwater fish.
Does aquarium salt kill bacteria?
Finally, it’s easy to accidentally overdose salt, which may kill everything (not just the bacteria) in your freshwater aquarium. Nevertheless, with accurate measurements and careful usage, both new and experienced fish keepers can benefit from this highly effective remedy. How Does Aquarium Salt Work? Salt essentially causes death by dehydration.