Using Salt, Which salt to use and how?
Do not ever use salt that contains the following: Salts that are not safe
YPS (Yellow prussiate of soda).
Anti caking agents especially those containing cyanuric acid.
Cow salt blocks or salt containing magnesium and other added minerals.
Iodine will actually not hurt the fish but it will harm your beneficial bacteria and cycle.
Salts that are safe
You can safely use rock salt, kosher salt, sea salt, synthetic reef salt, non-mineralised salt cow blocks, solar salt, water softener salt and some non-iodised table salts. Check the salt says 99.97% NaCl on the packet as a double precaution. All these salts should say exactly that. The added drying agent in some salts called sodium aluminosilicate is also not dangerous.
Some of these salts will produce carbonates & raise pH slightly. This is not good for tanks showing any ammonia at all. Make sure ammonia is zero before administrering salt.
None of these salts will damage your cycle at a strength of .3% and in fact possibly higher.
How to administer
Using salt at the medicinal dosage of .3%.
You will be adding salt at 3 x 12 hour intervals.
First of all make sure that the tank water is registering 0 for ammonia and nitrites. Nitrates should also be as low as possible. Mix the first dosage of .1 % of salt in a small bucket/cup with a small amount of treated conditioned water or tank water. This means one teaspoon per one gallon. So if you have a 10 gallon tank for example you are going to be adding 10 level teaspoons (one teaspoon is 5ml ) to the bucket or cup.
Mix the salt until it is completely dissolved. The warmer the water the quicker it dissolves. It can take 5 minutes or so. The salt must be completely dissolved before adding it to the tank. There should be no grains of salt visible, only a kind of shiny cloud is visible as you pour the salted water into the tank. Pour the salted water into a heavily aerated area of the tank...under the filter power outlet or fountain spray bar will provide the best circulation of the salt.
Leave the tank and fish for 12 hours. Remember if your fish are sick you are probably not feeding much and if they are stressed a dark cover on the tank can provide welcome shade and comfort. If you are treating for ich you will need to start to slowly raise the tank temp (no more than 2 degrees in an hour)aiming for a final stable temp of 80F.
After 12 hours repeat the dose. That is another 10 teaspoons for a 10 gallon tank pre-mixed as described.
After another 12 hours repeat again. This brings you finally to the recommended .3% medicinal dosage.
With minimal feeding/no feeding and pre tank water parameters at optimal levels you can safely leave the salted tank for several days while the salt gets to work. However if you are treating for parasites including ich it is very important that you do gravel vacs to remove parasite eggs that will be continuously falling on the tank bottom. (Bare bottom tanks are much easier to vacuum when dealing with parasites).
Remember with every gravel vac or water change you are going to need to replace the salt. So if you remove 1 gallon of water after a thorough vac, you will need to replace 3 teaspoons of tank water dissolved salt. It is a very good idea to keep a salt diary by the tank so you can track your salt content- how much is in there.
After the recommended time you can safely begin to remove the salt. This is done simply through water changes. If you add no more, gradually over several water changes all the salt will be removed.
So, I hope this info is useful to anyone who is about to use salt.