# aquarium salt and fish physiology: a very brief introduction



## RoyalBlueDarling (Nov 17, 2011)

Hello all,

I'm new around here, and have been trawling the forums. I've noticed a lot of comments stating that bettas can develop a tolerance/resistance to aquarium salt, and so have decided to post this in the hope that it will help people to understand the function of salt in the body. I should mention in advance that I am far from an expert on fish physiology. However, I am a medical science student, have noticed that fish are very similar to humans, and have done a little bit of research to confirm this. 

So, without further ado ...

Most chemical reactions in your body (known as metabolism) occur in aqueous solution. This is basically water with a bunch of ions swimming around in it. Or electrolytes if you prefer ("the ionized or ionizable constituents of a living cell, blood, or other organic matter"). A chemical soup. I know that some people will be more familiar with one word over another, and am trying to make this as easy to understand as possible, so I hope it's working, and forgive me if it sounds silly. 

For example, salt is sodium chloride (NaCl). When salt dissolves in water, it is broken into ions of sodium (Na+) and chloride (Cl-). Both play a vital role in the body's physiological processes.

Humans (and fish) have what's called a sodium-potassium pump. When this isn't working properly, your nervous system goes haywire, either working too much (giving off too many electric impulses/signals, which muck around with your muscle contraction--including your heart) or not enough (which also mucks around with your muscles by causing a lack of contractions).

If a betta were to develop a tolerance to aquarium salt, then their nervous system would not function properly, so you see this is impossible.

However, a betta (and a human) can be overdosed on salt (or underdosed, but this is much rarer), which leads me to the excratory system and the kidneys ...

The kidneys play a major role in removing excess salt and other stuff from the body. They do this by osmosis (in the most layman terms I can think of, moving water through semi-permeable membranes from one area of the body to another) and active transport. Everybody knows that when you eat salty food, you become thirsty. Your brain triggers a thirst mechanism, which makes you drink so that your kidneys can expel the excess salt via the urine. The reason that eating too much salt over time gives a lot of people heart problems is because drinking water increases fluid, thereby increasing the fluid in your bloodstream (where the excess sodium is), which in turn puts extra work on your heart by forcing it pump harder in order to shift the extra fluid around through your blood vessels. So, then you urinate to remove this excess fluid and waste. But if you do this too much, you end up with kidney failure as well as cardiovascualr disease.

Where bettas (tropical freshwater fish) are concerned, salt plays a big role in osmoregulation ("the maintenance of constant osmotic pressure in the fluids of an organism by the control of water and salt concentrations"), so again they cannot develop a tolerance or resitance to salt because it would mess with their osmoregulation, and this would either bloat them all over or dry them out like an aumtum leaf.

They can, however, develop kidney failure as a result of excess salt. As I said, I'm no fish expert, but a vet I know says that overdoing on aquarium salt is a leading cause of dropsy/kidney failure (the bloating all over water retention mentioned above).

It's interesting to note that just like humans, excess salt will cause a betta to drink and urinate more. (I found this out by reading a few online articles about the difference between saltwater and freshwater fish regarding the sodium-potassium pump. Apparently, saltwater fish drink saltwater to get enough Na+ and Cl-, and freshwater drink to get rid of the excess.)

So, I suppose what I'm trying to get at here is that:

a) a betta cannot develop a tolerance to salt, so don't think that adding salt to your water changes will somehow minimise the effect of salt as a medical treatment.
b) since salt does not evaporate (if you want to see what I mean, dissolve some salt into some water, and then let the water evaporate by boiling it, and you'll have salt crystals left at the bottom), it is possible to inadvertantly overdose your betta on salt if you add it to the water with every water change without monotioring exactly how much you're putting in.

Therefore/in conclusion, the method listed on the forum for treating bettas for fin rot (1 tsp/gallon, and not exceeding the treatment over ten days) is great, but people who add aquarium salt during every water change should be very careful not to overdose their little guys (and gals).

PS: Never substitute table salt for aquarium salt because table salt contains iodine, which has good benefits for humans, but is bad for fish.

PPS: If anyone knows more, or can explain it better, please add on to this in the comments. Thanks.


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## HatsuneMiku (Jul 29, 2011)

RoyalBlueDarling said:


> If a betta were to develop a tolerance to aquarium salt, then their nervous system would not function properly, so you see this is impossible.
> 
> So, I suppose what I'm trying to get at here is that:
> 
> a) a betta cannot develop a tolerance to salt, so don't think that adding salt to your water changes will somehow minimise the effect of salt as a medical treatment.


hi royal .. awesome information !! and welcome to the forums ..

to respond to the quoted lines .. the reason people post about not using aq salt daily and to only use it for medical purposes (10 days etc) .. just to clarify more on that information when tolerance is concerned .. is that it's not the betta that grows resistant .. it's the bacteria's that the salt usually kills .. that will build a resistance to the salt .. 

so for example if one was always using 1 tablespoon of aq salt per gallon to prevent bacterias .. if that betta were to get sick say due to fin rot .. they would need a double dose (2 tablespoons/g) of salt treatments to get rid of the bacteria's that have grown resistant to the 1 tablespoon/g water .. if that makes sense =D .. sometimes i ramble and it ends up not making sense .. 

i hope that clears up somethings about using aq salt for treatment purposes


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## Gloria (Sep 22, 2011)

Welcome to the Forum RoyalBlueDarling...
WOW!! That was very interesting to read. I actually undersood it  Again, it was VERY interesting and am glad you could give that information


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## RoyalBlueDarling (Nov 17, 2011)

HatsuneMiku said:


> hi royal .. awesome information !! and welcome to the forums ..
> 
> it's the bacteria's that the salt usually kills .. that will build a resistance to the salt ..


Hi, thank you. 

Yes, bacterium are nasty things that can build up a tolerance to pretty much anything. Thanks for adding that; it's very useful information and I didn't think of it at all. (I was too busy concentrating on betta tolerance!)


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## RoyalBlueDarling (Nov 17, 2011)

Gloria said:


> Welcome to the Forum RoyalBlueDarling...
> WOW!! That was very interesting to read. I actually undersood it  Again, it was VERY interesting and am glad you could give that information


Hi, thank you.  I'm glad you could found it interesting--I tried hard not to make it sound like a jargony information dump.


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## SmokeNLark (Jul 22, 2010)

That was a great explanation. It'll help people understand the consequences of constant salt use. I am a zoology student, and I know most of what you're talking about. The specifics are nice though. Easy to understand 
And yeah, the reason we treat fish with salt is usually because of bacteria, not the fish itself. Cuts, fin rips and other illnesses are usually caused (or prolonged/infected) by a form of bacteria, which is what we want to get rid of.


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## RoyalBlueDarling (Nov 17, 2011)

SmokeNLark said:


> That was a great explanation. It'll help people understand the consequences of constant salt use. I am a zoology student, and I know most of what you're talking about. The specifics are nice though. Easy to understand


Thanks heaps. 

I was worried about people overusing it after reading a few comments here.



SmokeNLark said:


> And yeah, the reason we treat fish with salt is usually because of bacteria, not the fish itself. Cuts, fin rips and other illnesses are usually caused (or prolonged/infected) by a form of bacteria, which is what we want to get rid of.


Yeah, I got so hung up on the comments I'd read about bettas "developing a resistance", I kind of forgot about the other side of the coin, which was bad.  But that's what the comments section is for.


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## Akeath (May 12, 2009)

With the bacteria and salt treatment, I remember reading about how that works and how tolerance to it works. (Don't remember which book it was, though). 
The jist of it is this:
The reason that salt kills bacteria is the _change _in salinity. That's why you add salt to a fresh water aquarium to kill bacteria, but in salt water aquariums you dip the fish in a fresh water bath to kill bacteria causing diseases. 
Focusing on the fresh water aspect, fish have several things they can use to control salt, if they are getting it in lower dosages for short periods of time - most of which were mentioned in the first post. 
However, the bacteria, which are unicellular, rely pretty much on just osmosis, that's part of being bacteria.
The bacteria can't regulate the salt as well as the fish, so when the ratio of salt water to fresh water changes suddenly (like when we add aquarium salt to the aquarium) according to the rules of osmosis all the water in their bodies goes out to the aquarium water where there is more salt in the solution and the bacteria shrivel up and die. Or the opp. happens in bacteria evolved in salt water when suddenly put in a fresh water environment, they have more salt in their bodies and the water rushes in due to osmosis, and the bacteria "explode". The fish have other mechanisms to handle it, and so in low dosages/time exposed (like 10 days) take no lasting harm from it. The bacteria and very basically built parasites don't have such good mechanisms and due to the way they are built are very unlikely to evolve them in timespans less than millions of years, so they are killed by abrupt changes in salinity, since they are too simply built as unicellular organisms to deal with that kind of change. 

So with the idea that the bacteria develop resistance to it: Their very unicellular makeup will work against them so that adapting to the sudden salinity change is extremely unlikely. However, keep brackish water consistently and they will evolve to the stable level of salt, as evolving to a stable water salinity won't take nearly as long as evolving to adapt to changes in salinity (it would have to get more cells, first off, and then these cells would have to get into organs and stuff like that...in the end it wouldn't even count as bacteria anymore). Whereas your fish, who lives much longer, would take many generations to evolve to deal with the brackish water, so will likely simply suffer kidney damage and die if you keep aquarium salt in there all the time.


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## RoyalBlueDarling (Nov 17, 2011)

Akeath said:


> However, the bacteria, which are unicellular, rely pretty much on just osmosis, that's part of being bacteria.
> The bacteria can't regulate the salt as well as the fish, so when the ratio of salt water to fresh water changes suddenly (like when we add aquarium salt to the aquarium) according to the rules of osmosis all the water in their bodies goes out to the aquarium water where there is more salt in the solution and the bacteria shrivel up and die. Or the opp. happens in bacteria evolved in salt water when suddenly put in a fresh water environment, they have more salt in their bodies and the water rushes in due to osmosis, and the bacteria "explode".


Yep--bacteria are prokaryotic. Your explanation is excellent, thanks for adding it. A good comparison is what happens to the bacteria is what happens to cucumbers when you pickle them.

The adaptation to the salt ... It works the same way as superbugs, I suppose (like MRSA). I'm not sure because I haven't got up to that in my studies yet.


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## 1fish2fish (Sep 10, 2009)

Very nice explanation. I've been working on an article for my blog that I was going to also post here on the uses of aquarium salt and epsom salt, when and when not to use it, etc but haven't had time to work on it lately.

My take away... If your betta isn't sick.. Don't use salt. Don't fix what's not broken and generally speaking clean water is all the prevention you need.
_Posted via Mobile Device_


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## SnowySurface (Apr 25, 2011)

RoyalBlueDarling said:


> PS: Never substitute table salt for aquarium salt because table salt contains iodine, which has good benefits for humans, but is bad for fish.
> 
> PPS: If anyone knows more, or can explain it better, please add on to this in the comments. Thanks.


I just wanted to mention that no one should use the Sea Salt you can buy from the store for cooking. It may not have iodine in it like most table salts, but I still think there is a difference between aquarium salt and the sea salt you crush from a shaker. I know I don't season my food with aquarium salt, so I'll assume I shouldn't treat fin rot with my seasoning salt. XD 

I also doubt there is anyone who could explain how salt affects fish better than this. Thanks for the info.


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## dramaqueen (Jul 7, 2008)

Very good info.


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## Oldfishlady (Mar 1, 2010)

The Iodine in salt is in the form of Iodide and will not harm salt tolerant fish and can even be beneficial in small amounts, but the anti caking ingredients can sometimes be toxic in high doses, cloud the water, cause algae bloom and that should be avoided for those reason.

Aquarium salt (Sodium chloride) is a great product to use for short term treatments in salt tolerant fish when used for the right reason, in therapeutic dosages and duration. But this is true for any product especially OTC antibiotics-over use, misuse, used for the wrong reason, dosage, duration etc......often can cause more harm than good....


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## Myates (Aug 2, 2011)

This, or one similar would be a good sticky- as I see too often people recommending others to use AQ salt needlessly and without the proper amounts/water changes to go with it. This is a good reference to send to others in a way to explain the use/benefits/risks in using AQ salt.


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## RoyalBlueDarling (Nov 17, 2011)

Oldfishlady said:


> ... especially OTC antibiotics-over use, misuse, used for the wrong reason, dosage, duration etc......often can cause more harm than good....


Yep. Just like in humans, again. If you don't follow through with the entire antibiotic treatment, all you are doing is giving the bacteria a chance to develop a resistance to that strain of antibiotic, because not completing the treatment will ensure that some bacteria survives, and the surviving bacteria will become resistant to the antibiotic you have used (e.g. tetracycline), and next time around you won't be able to fight it off so easily.

Also, keep in mind that antibiotics are excreted primarily by the kidneys, so overdoing it, especially in combination with aquarium salt, could give your little guy or gal kidney damage or failure, which will lead to water retention/dropsy, and this is the fatal kind of kidney damage, not the bacterial kind that if caught early can be treated, since you can't give a fish a kidney transplant.


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## RoyalBlueDarling (Nov 17, 2011)

*Addendum: Combining aquarium salt with meds.*

After OFL's comment, and my comment on antibiotics, I started thinking about all the people who combine aquarium salt with meds.

Don't do it.

Or check the MSDA (material safety data sheet) first. 

A lot of meds (e.g. Jungle Fungus Eliminator) already come with a lot of salt added, so by adding your own dose of aquarium salt, you are overdosing your fish.

I've noticed that most Jungle products contain salt.

If you don't know whether a product has salt added, check for "sodium chloride" on the bottle. Unfortunately, sometimes there is nothing on the bottle, it's just Mystery Solution X to combat so-and-so.

Also, please _don't mix aquarium salt with antibiotics_. What you are doing is making a chemical soup, and if you don't know how the two might potentially react, it's best not to turn your fish into a lab rat. Swimming around in the stuff as it decomposes is not the same as you popping an antibiotic and then washing it down with a cheeseburger and a Coke.

Anyway, I hope this little addendum is useful.


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## 1fish2fish (Sep 10, 2009)

Its always best to only use one medication unless you know for a fact that two can be used simultaneously (like Marycn1 and 2). 


Same goes for people....


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