salt: snake oil or science - Tropical Fish Keeping - Aquarium fish care and resources
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post #1 of 7 Old 10-26-2012, 08:42 AM Thread Starter
salt: snake oil or science

I have read that salt used in freshwater aquariums can reduce ammonia or nitrite toxicity and reduce stress, improve fish health.
Osmoregulation refers to the physiological mechanism fish use to control the amount of salt and water in their bodily fluids. The implication is freshwater fish are saltier than the water they live in so fish release bodily salts and take in water. Freshwater fish use special cells in their gills to take in the salts as chloride that is lost to the water.

When freshwater fish are stressed they suffer from osmoregulation dysfunction which is the loss of bodily salts to the water column. Adding salt in times of stress can help reduce the lose of bodily salts and correct the osmoregulation dysfunction. Salt also can reduce toxicity of pollutants and kill some pathogens (gill and skin flukes).

Ammonia has two forms in water, ammonium and free ammonia. Free ammonia is very toxic to fish and ammonium is much less toxic. There is an relationship between free ammonia and ammonium and this ratio is dependent on ph, temperature and the amount of salt in the water column, as salinity increases the total amount of free ammonia decreases.

Salt is a substance containing sodium and chloride. chloride should reduce the toxicity of nitrite by providing chloride ions that offer some protection to the fish. "For counteracting the effects of high nitrite, just 100 mg (0.1g) salt per litre is enough. This very low salt level is tolerated by virtually all freshwater fish, even catfishes."

Is this snake oil or should I try this science.

Frequently asked questions on using salt | Features | Practical Fishkeeping

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post #2 of 7 Old 10-26-2012, 09:27 AM
Just my $.02....
I've always applied the KISS method and looked at it very simply. Freshwater rivers, lakes, ponds etc. do not contain salt, so neither should an aquarium.
I suppose in some extreme cases where some parasite or disease is being treated, salt may be as good or better 'medicine' than some chemicals, but otherwise, if it's not a brackish or SW tank, leave the salt in the cupboard.
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post #3 of 7 Old 10-26-2012, 10:21 AM
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Only freshwater tropical's that I would consider the use of salt with ,would be Mollie's who do seem to do better with slightly brackish water. 1 tsp per 5 gal. has worked for me in the past with this species.
As for salt's ability to help detoxify nitrites,ammonia, I would submit that water change is much quicker to have the desired effect.

The most important medication in your fish medicine cabinet is.. Clean water.
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post #4 of 7 Old 10-26-2012, 02:12 PM
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Salt is bad! It will kill your fish and plants.
It doesn't promote healthy gill function or improve slime coating. All it does is stress out the fish.
The only time I would ever consider using it is when treating disease (especially ick).

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post #5 of 7 Old 10-27-2012, 05:48 PM
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The argument over aquarium salt in a freshwater aquarium will probably be around forever, because while there are cases where it can help something such as nitrite, and certain parasites if the salt is in sufficient amounts, there is also the irrefutable scientific evidence of its harmful effects on many if not all freshwater fish. The omoreguation aspect you mentioned is one clear case of where salt is negatively affecting the fish, and if continued can kill it.

I researched this topic extensively a while back, and wrote an article in our freshwater articles section--which few seem to ever remember--here is the link:

Pop, you should have a look at the articles, you may find others of value.


Byron Hosking, BMus, MA
Vancouver, BC, Canada

The aquarist is one who must learn the ways of the biologist, the chemist, and the veterinarian. [unknown source]

Something we all need to remember: The fish you've acquired was quite happy not being owned by you, minding its own business. If you’re going to take it under your wing then you’re responsible for it. Every aspect of its life is under your control, from water quality and temperature to swimming space. [Nathan Hill in PFK]
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post #6 of 7 Old 10-28-2012, 10:01 AM
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Add my vote to the never use salt crowd.
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post #7 of 7 Old 10-28-2012, 10:03 PM Thread Starter

hello friends,
Shooting from the hip I have to agree with the suggestions posted above using salt on a regular basis is not good for the freshwater aquarium. In the article Salt in the freshwater aquarium points out one teaspoon of salt will reach a portion of 60 ppm in a 16 gal tank and this amount will cause stress and suffering. From what I have read this is correct.

My interest concerning salt is at a much reduced volume of about one or two parts per million guessing about ½ teaspoon of salt to say 60 gallons of water. I think diminishing returns would apply with reduced concentration of salt the greater the diminishing of listed effects, maybe not.
At this point I must point out the following idea is not based on fact or truths of any type. It is the sole results of an idea that occurred to me while reading about salt usage. Since we fish keepers wear many different hats (paradigms) let us change hats and look at this with our reductionist hat on, Osmoregulation and (CL) molecule.
Osmosis works the same way for fish as it will for a filter. Osmoregulation is osmosis at work: water passing through special permeable membrane of a cell into the fish’s body. The way it works is water molecules goes through the cells into the fish’s body where there exists higher concentration of solutes such as body salts, nitrates or nitrites maintaining osmotic pressure ( meaning an exchange of solutes). Osmotic pressure is the pressure exerted by water on the fish’s cells to keep in balance the amount of solutes equal in both inside the fish’s body and the water the fish is swimming in. (I think this is how fish uptake things like nitrate, nitrites and ammonia.)
Within a fish’s blood there exist the CL molecule and this chloride ion is neutrally charged and due to osmotic pressure the sodium and chloride ions in the fish match the levels of salt in the aquarium water, if there is a concentration of nitrites or nitrates or ammonia in the water osmotic pressure will also attempt to reach a balance between the fish and environment.
Getting back to the chlorine ion that is neutral charged, it has the ability to resist the osmotic pressure to balance nitrates and nitrites between fish’s body and the water. What this may mean is that chlorine ion will stop the uptake of nitrites and nitrates and coupled with water changes will produce an artificial conclusion to the nitrogen cycle.
I know we are taking a giant leap of logic but think of deep sand beds. What do these bacteria do? It breaks down nitrates into what compounds nitrous oxide gas and the necessary neutrally charged chlorine ion. This is the natural conclusion to the nitrogen cycle.

I don’t know how I ended up thinking about the nitrogen cycle. There are several problems with this idea just put forth.
One is there exist a ratio of 3 to 1 between CL neutral charge ion and nitrate or nitrite in the water to resist nitrate or nitrite uptake by osmotic pressure. To achieve this necessary ratio could require salt levels that may injure aquarium occupants (both fish and plant).
Another error is the artificial and contrived ending of the nitrogen cycle is equal to the normal, natural and expected end of the nitrogen cycle.
Snake oil or science maybe a little of both, I think I will put in a deep sand bed.
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