There are multiple reasons to use salt 

and so, there is no one answers to the amount of salt that one should have in their pond. The primary reasons are physiological need, anti-parasite, and stress-relief. There maybe others and I am sure someone will remind me...

Let's understand sodium chloride in relationship to the physiological needs of the fish. Sodium and chloride ions are taken up by the fish separately by special cells (chloride pumps) in the gills. The fish uses chloride to help maintain the chloride level of the blood (.9%) and this level of chloride is used to remove ammonia from the fish's system. At the gills, there is a gas exchange where O2 is taken up and ammonia released into the water. This is why we say that about 65% of the ammonia in the water is from respiration, not urine output. Fish use urine output to rid itself of excess water primarily and a little ammonia goes with it. It is chloride in the system that pushes the excess water out through the kidneys. So, you can see that chloride is SO important to the fish that it has special cells that do nothing but manage chloride processing.

Sodium is one of the essential physiological mineral needs of the fish all by itself. If is because of the availability of sodium chloride in nature (and Home Depot) that makes it our best way to get chloride into the water. We could also use potassium chloride or calcium chloride to accomplish the same thing but because the ratio of sodium to potassium and calcium need is so much higher, sodium chloride is our best bet. BTW: I use all three in q-tanks with fish in bad shape from deep ulcers where I fear electrolyte loss or other reasons for physiological imbalance.

Mother Nature satisfies the fish's physiological need for chloride by making it available in fresh, natural water. She provides "salt" levels of .02 to .1% (depending on where you live) in fresh water fed through aquifers and such. I have tested fresh water from all over the country and found this range of salt in natural waters. For the most part, a range of .06 to .08% seems to be the norm.

Now, check your city water supply and see what it is.. mine is .035% and to me, that is too low so I raise mine with regular old Morton Salt in the blue bag from Home Depot. I do not think that salt levels are a critical measurement and so from time to time I check the level and add whatever I think gets it "close" enough to .06-08%. And this is fine for healthy ponds and healthy fish.

Any arguments on physiological need???

Now, salt for anti-parasitism (do we make these words up??).. I am really not convinced that for the average ponder, that the "overuse" of salt has caused salt-resistant parasites. To breed these salt-tolerant monsters requires a generation over generation morphing of the physiology of the parasite. Is it possible..absolutely... consider why chickens are birds and don't fly... I am reasonably convinced that some breeders, who maintain closed environments, have created "salt-tolerant" parasites because of their breeding and husbandry practices. For those bugs to get to our ponds would require those breeders to ship parasite-laden fish to the public (and we KNOW that never happens). So, while I agree that the possibility exists, just how wide spread is it?? Someone prove it to me.

That leads us to using salt for parasite control as a practical treatment plan. There are those that are espousing that salt no longer works and I disagree....just because we don't know the reality. Consider that salt is still the least noxious (to the fish) of the treatment options available to us. I would much rather irritate a fish with salt than irritate a fish with formalin or malachite green. And with salt, we do not have to consider other water parameters, like temperature, pH, ammonia, etc. I particularly like salt baths as a first step to dealing with a fish in trouble. The level I use depends on the condition of the fish but I never use something higher than .6% unless I am 100% sure it is costia. There are far more people out there that do not have microscopes and so they are guessing on the problem and frankly salt gives them a cheap, reasonably effective, and SAFE treatment option. If it does not work, then we have learned something. If it does work, then we have saved the fish from an introduction to something like formalin or MG.

And I still recommend a salt level of .3% in the early spring and late fall for a couple of weeks as a prophylactic treatment against parasites. We all know that the parasites start earlier and stay longer as the water temps raise and then dip outside the fish's ability to handle parasite attacks. No one can argue this. You can argue all you want that .3% won't effect parasites anymore but if you do, convince me (and yourself) that the only parasites in your pond are salt-tolerant and that birds and other creatures have not deposited other parasites into the pond. It happens.. everyday.. and going into winter, a salt treatment just makes good sense to knock down the parasite load as the water cools.

And finally... salt for stress relief. I already introduced how salt is required by the physiology of the fish. This now becomes a given in the effort to reduce stress. We have talked a ton about osmo regulation but this is a complicated process. Increased salt levels in the water not only make more chloride ions available to the fish but also reduce the surface tension of the water against the cells that take the ions up. By reducing the surface tension, these cells can more effectively "absorb" and exchange the ions with the water. This is the premise of osmo regulation. And by doing this, we can reduce the stress on fish by simply making it easier to "breathe." A rough parallel is the use of pure O2 on stressed humans as this gives the body a better chance to function properly.

I recommend salt baths as the first treatment process for dropsy symptoms mostly to see if the fluid retention is caused by a break down in the osmo process. Bad water, stress, etc can cause the osmo process to breakdown and force the fish to retain fluid as the lack of chloride ions restricts the ability for the fish to expel these excess fluids. Do not confuse this with fluid retention due to organ damage. The problem is that we do not know what is happening when we first see dropsy symptoms so a salt bath makes perfect sense as a first step. Arguments??

So, you can see that "salt" is a more complicated issue than whether parasites are tolerant to its effects or not.. it is a physiological need of the pond and the fish. I agree that it can be an irritant when used wrong but consider all of the things it can do for your pond and fish.

REC
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