Is Salt Beneficial?

[K.J.]

Now I'm sure this is in the wrong section, so if mods feel it needs to be moved - feel free to move it! But I figure some scientific depth on the subject might help people who want to add salt to their water. I know this was discussed in the betta section, but I'd like to see some science geeks (just kidding!) debate over it.

So, basically what I'm asking is: would adding typical aquarium salt help AT ALL with fin rot, etc, or is it just a big scam?

(sorry for lack of "scientificamul" evidence, I have no idea how to debate in here so I'll let the pros take that course.)

 

[Tokis-Phoenix]

Salt can kill off certain parasites and may help heal bacterial anf fungal infections in fish, but it can be a double edged sword, as for many freshwater fish it causes a great deal on stress on the fishes internal organs at the same time it is helping the fish.

Fish have an osmotic pressure greater than that of the fresh water around them and in order to maintain that pressure they must keep agreater concentration of salt internally than what is outside of them. This is only true for freshwater fish. The reverse is true for saltwater fish. Increasing the ammount of salt that a freshwater fish is exposed to will result in the fish becomming dehydrated. The freshwater fish is designed to expell water and hold salt so if you increase the salt levels above what the fish hold internaly it will pass out more water than it asorbs. The result is a strain on the internal organs, and possible liver and kidney failure, and kidney stones. Freshwater fish urinate constantly to maintain the ballance of water in their system. Salt water fish do the reverse they drink saltwater to regulate
their osmotic pressure. In saltwater the water is constantly trying to pull water out of the fish, and in freshwater a fish is constantly pulling water in from a freshwater source. You can do great long term dammage to your freshwater fish by using salt for long periods of time.


So salt should only be used in emergency situations where;
a. It is the most effective medicine for treating the problem at hand.
b. The fish it is been used on are not particularly intolerant of salt.
c. It is only used for a short period of time.

The only fish which as a species seem not to suffer than much from salt use are livebearers and certian labyrinth fish, most other freshwater fish are very negatively effected by salt- always remember that they are salt alternative meds for every fish problem you can think of, so there are no situations where you should be forced to use salt to treat a fish problem.

More info on salt use on fish;

http/www.marietta.edu/~mcshaffd/aquatic/...ant/excrete.htm

 

[OohFeeshy]

I said on another thread that I think part of it is an almost placebo effect- minor infections and wounds can often be easily overcome by the fish itself (things like damaged fins on a betta), and it's all too easy to put it down to salt you've put in the water. You're also more likely to keep the tank clean when there's disease about, which also helps.

 

[Fella]

I don't have any evidence to hand, but I believe it to be true that with salt in the water, it can reduce the toxicity of the nitrogen cycle. Don't take that as gospel though, i'm sure someone will have evidence on that far greater than anything I can dig up if it is true.

 

[Invader Xan]

I have the personal experience that salt is very good at killing off aquatic fungi. I had some trouble with water mould when my tank was first cycling (damn cheap mopani). Raising the tank's specific gravity to about 0.05 with marine salt killed off the majority of the mould until the tank's biofilm had a chance to develop properly... In fact, I read somewhere that there are very few marine fungal species because fungal cells tend to be highly intolerant of saline conditions -- though I'm afraid I have no references for that fact.

In short, it's reasonable to believe that salt can assist with fungal ailments, though it's probably less effective with bacterial problems. I don't see any possible mechanism for salt to help with viral infections... though I don't know very much about viruses.

Like Tokis says though -- if your fish can't tolerate salinity, you'll probably do more harm than good.

 

[Musho3210]

I don't have any evidence to hand, but I believe it to be true that with salt in the water, it can reduce the toxicity of the nitrogen cycle. Don't take that as gospel though, i'm sure someone will have evidence on that far greater than anything I can dig up if it is true.

yeah i heard salt lowers the toxicity of nitrite.

 

[Mordinbar]

There is one other positive benefit to salt in aquaria, but as Tokis said, I dont think it justifies using it as a regular additive. When fish are 'breathing' or moving water past the lamellae in their gills, oxygen is absorbed by two means, osmotic pressure, and counter circulation of the blood stream, so that the highest level of oxygen in the water is always exposed to the blood with the lowest amount of oxygen, this allows fish to absorb the highest amount of oxygen they can. One of the major limiting factors in oxygen absorption is the presence of carbon dioxide. Just as in an aquarium, the more carbon dioxide present the less oxygen.

When cells respire, Oxygen is turned into CO2 and carbonic acid is formed from the reaction of the CO2 and the water, but the rate of diffusion of the acid is very slow. Therefore fish have developed a mechanism to force the expulsion of carbon dioxide through the use of Ionic (chloride) pumps in specialized epidermal cells. Essentially these Chloride pumps pull in an external Cl- Ion and swap it for the H2CO3 molecule that the carbon dioxide formed when it passed out of the bloodstream.

The chloride ions are necessary for the fish to properly respire, but the concentration of them is plenty in general water.
*Note the fact that in distilled water there are NO essential elements or ions, and this can actually cause suffocation of the fish, along with other metabolic deficiencies. Which is why pure distilled water is unfit for fish.

 

[Bignose]

There is one other positive benefit to salt in aquaria, but as Tokis said, I dont think it justifies using it as a regular additive. When fish are 'breathing' or moving water past the lamellae in their gills, oxygen is absorbed by two means, osmotic pressure, and counter circulation of the blood stream, so that the highest level of oxygen in the water is always exposed to the blood with the lowest amount of oxygen, this allows fish to absorb the highest amount of oxygen they can. One of the major limiting factors in oxygen absorption is the presence of carbon dioxide. Just as in an aquarium, the more carbon dioxide present the less oxygen.

Nope, osmotic pressure and oxygen are completely unrelated. Osmotic pressure is a function of the dissolved salts and minerals in the water, not the oxygen.

Also, the levels of dissolved oxygen and carbon dioxide in the water are so low in typical situations (including aquariums) that they don't limit each other. The aquarium's top where the water is exposed to the atmosphere is enough to balance the dissolved gases very quickly. Consequently, the low amounts that are actually in the water don't hinder the dissolution of either of them. There has to be very high concentrations before any limiting can occur. Such high concentrations are exceptionally rare in nature and home aquaria.

 

[Mordinbar]

I meant to write in a diffusion gradient instead of osmotic pressure >.<... And while in he water itself the chances of CO2 limiting the amount of DO is low, the potential in the bloodstream is still there. As soon as most of the hemoglobin in the blood is bound up with oxygen to remove it from the concentration gradient, you run into CO2 limiting, due to a principle known as The Root Effect (the capacity for CO2 to decrease hemoglobins binding affinity for O2). So while there is no direct 1:1 lmiting of oxygen, it can occur.

I apologize, I should have been more clear earlier.