I got a very interesting comment today about the use of salt in ponds. It was sent by Erlank and here's his note to me:

"Hi, please put a highly visible banner in your website stating: "NEVER EVER USE TABLE SALT!!!". Salt (sodium chloride) is NOT a proper way to suggest that only PETSHOP COURSE SALT should be used...WITHOUT IODIUM (Iodine is the english version).

I'm a beginner with Koi and didn't know the difference yet between table salt and sodium in conjunction what it will do to one's Koi fish!!! Please put a caution against TABLE SALT and clearly state the differences in relation to fish pond use..."

Erlank brings up a very good point and the caution he suggests is not quite right. In fact the only reason I can think of as to why this suggestion may have been made to Erlank is because someone wanted to sell some salt.

The Facts About Salt ... and therefore Salt in Koi Ponds

Salt has the chemical name Sodium Chloride and the symbols NaCl ... it can be produced in the laboratory by reacting hydrochloric acid with sodium hydroxide but this is not recommended since the reaction can be very vigorous. The Cl (Chloride from Chlorine) in NaCl is a very close compound to Iodine.

Salt is not made in the normal sense of the word it is rather recovered in large evaporation dams (called salt pans) where salt water (not necessarily sea water) is allowed to concentrate. In South Africa where I live there are many such salt pans and they work well because we have very low humidity and much sunshine.

After a certain concentration of salt in the water is reached the salt precipitates and is harvested and then refined. Many people who watch National Geographic programmes will have seen massive flocks of flamingoes congregating around salt pans in the Great Rift Valley of Africa. These birds feed on brine shrimps.

Salt therefore in practice is more than NaCl since other salts also precipitate with the NaCl. These other salts are perfectly safe to humans and therefore to most other forms of wildlife. Raw salt as distinct from refined table salt is used extensively in animal feeds because it is cheaper.

Table salt is perfectly safe to use in koi ponds and potentially safer than raw salt which could have any sort of contaminants in it by virtue of the process sued to recover salt and as explained above.

So What About Iodine in Table Salt?

First of all... Iodine is an element that is critical for normal function of the thyroid gland in humans.

Iodine (as Potassium Iodide ... KI)  is added to table salt in tiny proportions (about 0.006%) to counter possible iodine deficiency. This type of table salt is known as IODIZED table salt. Not all table salt available is IODIZED. If it is it will be identified on the label.

If anyone does have a real concern about using table salt for a pond then this concern can be easily overcome by buying non-iodized table salt. Maybe it is even preferable but I am quite sure no-one has ever done enough study to prove the matter one way or another. So you have to make your own mind up.

When it comes to adding salt to ponds no-one has ever convinced me that it is important. However it can be very important when used under strictly controlled conditions in a salt bath. See this article about using salt to treat parasites on fish.