Sorry this took so long but I was goofing off for more days than I should have been... we all suffer most AFTER vacation.
Let me start with George's comment about sodium and calcium. From a pure physiological requirement, sodium is required MORE by the fish than calcium. That simply means that it uses more sodium than say, calcium or potassium. Sodium, potassium and calcium make up the three primary "salts" or electrolytes in fish and mammals and we need to pay some attention to their presence in the pond. Although, a good koi food and a natural salt level in the water (.02-.1%) typically provides all of the mineral salt content the fish need.
When dealing with a severely ulcerated fish in quarantine, I will raise the sodium, potassium, and calcium chloride levels in the water in an effort to help the fish restore lost electrolytes. If you are familiar with Ringer's Lactate, used by medical people, the concept of electrolyte replacement is exactly the same.
Iodine in salt, such as iodized table salt, does the fish absolutely no harmless to fish and the beneficial bacteria in the pond. The only reason NOT to use iodized salt in a pond is the cost (and the problem with lugging around a huge number of one pound boxes of the stuff). There is not enough iodine in iodized salt to affect the bacteria even at .6%.. I know this, I tested it.
No matter what kind of salt you use, you will see some level of foaming when large amounts are delivered to the pond. It just happens.
Water softener salts with additives to prevent rust and corrosion, such as YPS, are potentially deadly to fish. YPS, yellow prussate of sodium, when exposed to UV (like, sunlight) produces arsenic in the water. Not a good thing. Anytime we are dealing with something unnatural from the perspective of what we would reasonably find in natural water, is a red flag to us, so, stay away from water softening salts with any kind of additives. Period.
Someone asked about calcium carbonate. If I am not mistaken, calcium carbonate is precipated out by the presence of calcium in the water. This process affects the pH level. I do know that Calcium chloride is an excellent addition to the pond to raise the GH levels which in turn stablizes (and in some cases, lowers, the pH). I know this drives Jnorth crazy, but on KoiVet is a thread about calcium chloride use in ponds with great info from Dr Roddy Conrad on it. The text of thread deals with lowering pH levels (in the 9's) by properly adjusting the GH (calcium hardness) and KH levels of the pond. It is interesting. Here is the URL
http://www.koivetforums.com/forums/s...ad.php?t=20827.
What did I miss??
REC