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Salt use in Freshwater Aquariums


By Carl Strohmeyer-PAMR 35+ years experience

Aquarium Salt (Sodium chloride) in Freshwater Aquariums
Updated 9/28/15

Magnified sodium chloride crystalThe use of Sodium Chloride more commonly known as plain salt seems to be a constant source of controversy among aquarists, especially here on the internet. What is interesting to me and my colleagues in the professional aquarium maintenance, design and research business is that the way this controversy has “swung” from "you MUST use salt" to the now current fad propagated by many forums and articles, to "RARELY or NEVER use salt".
Unfortunately, both views are based on misunderstandings of the term of what salt is and what fish need “salts” for, as well as a lack of understanding and reading of research about this subject.

Please read the article in full, including the myths/truths section.

What is “Salt”

I will start with some basic definitions of what “salts” are. Further reading beyond this article is needed here, so please follow links/resources/references.
Basically, a salt is a neutral compound composed of cations (positively charged ions) bound to anions (negatively charged ions).
A more in depth description is that “salts” are ionic compounds held together by electrostatic attraction of positively charged metal cations and the negatively charged anions. These Ions can be simple molecules, as in sodium chloride, or more complex groups such as calcium carbonate.
What I am driving at is that salts consist of more than just Sodium Chloride (what we generally refer to as salt is sodium chloride), and salts in general are IMPORTANT electrolytes necessary for biochemistry and osmoregulation in fish. Without salts fish and other biochemical processes would cease.

Please reference these two articles for further reader as to this subject:
*AQUARIUM CHEMISTRY; How to maintain a Proper KH & PH, why calcium and electrolytes are important.

Common salt-forming cations applicable to aquarium keeping include:

Common salt-forming anions applicable to aquarium keeping include:

Referenced/Sources from: What are Salts; Wikipedia

Sodium Chloride and other Salts in Aquariums

Salt, NaCl crystals This where the controversy begins in my opinion. The question is, should aquarium salt (sodium chloride) be used and if not, what will take its place for necessary electrolytes?
First, I will start off by stating again that ALL living organisms need certain electrolytes for biochemistry. The before mentioned resources help explain this fact).
I have read many scientific studies as well as performed many experiments over the years in the use of different salts including sodium chloride.
I will start by stating that a successful aquarium CAN be kept without sodium chloride HOWEVER, other "salts" MUST be present such as Calcium carbonate, otherwise your fish will have lower disease resistance and other physiological problems.

As a generalization when it comes to sodium chloride salts, I have found 1 tablespoon per 5 gallons works safely as a preventative for many community aquariums. However in most community aquariums, I have found in experiments in multiple aquariums, keeping almost no salt but then adding salt at a tablespoon per 5 gallons or higher when any possible issues arise or new fish are added works best (keeping in mind salt is not a cure all).
For therapeutic levels in aquariums or baths, 1 Teaspoon per one gallon is a good starting point (it can be higher in many cases).

Where this gets controversial is with freshwater Plants, Catfish, Elephant Nose, Tetras, Goldfish and Livebearers such as Mollies.

Starting with each of the above, let’s take a look them specifically:

A Few Facts, Uses and Myths About Salt in Aquariums

Some Suggested Salt Sources for when salt is used in a freshwater aquarium:


Often salt amounts are given as mg/L, however milligrams is a measure of weight while most of us use dry measurements such as teaspoons or tablespoons which are measurements of volume. So the average weight of salt must be found before converting.
To convert 1000 mg of salt into a given volume (in this case, teaspoons), you would need to find the average weight per this volume, which in this example is .22 teaspoons per 1000 mg (approximately).
This means that if your treatment required 2000 mg/L you would need .44 teaspoons of salt per liter of water. Since 1 gallon= 3.785 liters, you would need 1.66 teaspoons per gallon of water.
Many salt treatments call for as much as 3000 mg/L which means you would need approximately 2-1/2 teaspoons per gallon.

A few more conversions:

SUMMARY; Further Information about Salt use, both Positive and Negative

I will sum this up by saying that those who say you should not use sodium chloride salt in your freshwater aquarium (including with Catfish, Tetras, etc.) and those who say you should always use salt (NaCl) are only HALF RIGHT!
I would certainly agree that there was (and still is) a segment of the aquarium keeping hobby that thinks sodium chloride is the cure all for everything all the while ignoring important other “salts” such as Calcium Chloride.

However the current “No Salt” fad propagated by many poorly researched articles/blogs/ocial Media posts that sadly come up in Google Searches also ignores certain facts not only about sodium chloride but about the other important electrolytes as well.
While many fish such as Tetras do well without any added salt but for occasional treatment levels or baths, other fish such as Goldfish have been proven to to be more disease resistant with small amounts salt present along with even more important positive mineral ions of elements such as calcium.
My own years of experience and tests along with research and many of my professional aquarium keeping colleagues bears this out.

When salt is used the use of iodized table salt that is often found in kitchen cupboard is not the best choice, however in a pinch it is not a terrible choice as is often described (another aquatic myth).
If the small amount of salt that is needed in a freshwater aquarium is used the iodine (which is also a necessary nutrient for fish in small quantities as in humans) is not likely to cause any problems (due to the trace amount of iodine present after dilution in water).

Common table salt also has anti-caking agents such as sodium alumino silicate which is main reason to avoid table salt as this ingredient may cause increases algae growth (other anti-caking ingredients include potassium ferrocyanide and calcium carbonate).
Table salt is usually fine for short duration dips or baths, I would simply not recommend using table salt long term in an aquarium due to build up over time of anti-caking agents & iodine (assuming iodized salt).

I prefer to use either plain rock salt (water softener salt), marine salt (of which the additional major and trace elements are actually beneficial to many freshwater fish), or products such as SeaChem Cichlid Salt which (similar to marine salt in concept) contains added minerals/electrolytes of which when used in the small amount of salt one should use sodium chloride are actually beneficial for the vast majority of freshwater fish.

Product Resource: SeaChem Cichlid Salt; All Freshwater Fish Safe However, I do want to clarify that I recommend the use of plain salt (such as regular aquarium salt, water softener salt, etc.) for use in salt and medicated baths over marine or Cichlid salt as the later two add other elements that although essential in the general environment, they could dramatically alter the difference in the bath water and display tank water so to cause osmotic stress/shock.

Another point as to the use SeaChem Cichlid Salt or Marine salt in freshwater aquariums is that these salts BOTH add carbonates/bicarbonates (for KH) and in general many freshwater aquariums need not or even should not be used with buffers that also increase carbonates/bicarbonates.
The use of these two salts is fine with products such as Wonder Shells as these mineral blocks tend to dissolve as minerals are depleted and combined use is highly unlikely to increase GH/mineral levels to anything remotely dangerous for ANY freshwater fish.
In African Cichlid tanks I have often combined buffers AND Cichlid Salt, however I recommend monitoring KH and pH so as to find the “sweet spot” as to the correct amount of each to add so as to keep correct parameters (again the use of Aquarium Mineral blocks such as Wonders Shells is not a concern and I in fact strongly recommend this!)

Other Related Resources/References:

*Freshwater Aquarium Basics
*Fish Osmoregulation
*Aquarium Redox

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