Alright, I have questions about SALT in fresh water tanks. So I figured I wasn't the only one and would help answer for others. Hopefully this will get populated and become a sticky.
Aquarium Pharmaceuticals Doc Wellfish's Fresh Water Aquarium Salt
A small amount of this all-natural “salt” for freshwater fish will reduce electrolyte loss caused by disease and stress, and promote healthy gill function. It does not evaporate and is not filtered out. Also ideal for
Goldfish bowls.
Here is a resource for the salt at about.com:
http://freshaquarium.about.com/cs/tr...ltiinfresh.htm From above resource: When To Use Salt
Nitrite Poisoning - The addition of one half ounce of salt per gallon of water is beneficial in the prevention of nitrite poisoning in a newly set up tank.
Keep in mind that scaleless fish cannot tolerate much, if any, salt. Parasites – Many parasites can be effectively treated with the use of salt, particularly Costia infestations.
When Not To Use Salt
Live plants - If you have a tank with live plants, avoid using salt. Plants can be damaged with a relatively low dosage of salt, which is one reason its best to treat sick fish in a hospital tank rather than your regular tank.
Scaleless fish – Scaleless fish, particularly cordydoras, are very sensitive to salt. Even a small amount could harm them. Tetras are also fairly sensitive to salt. Contrary to popular view, it is not advisable to add salt to your aquarium on an ongoing basis unless the fish require brackish water conditions.
Performing a Dip (How To: Dissolving the Salt)
When treating parasites, a dip is the method of choice. Place 4 teaspoons of salt in a clean bucket, then slowly add one gallon of water from the aquarium, swirling it to dissolve the salt. Once the salt is completely dissolved, place the fish in the bucket for five to thirty minutes. Observe the fish closely, and if it exhibits any signs of distress, return it to the original aquarium immediately.
Performing a Bath
A bath is useful in treating an entire tank for prevention of nitrite poisoning, or for reduction of stress.
For stress treatment, measure out 1 teaspoon of salt for each gallon if water in the tank. Using a small container, dissolve the salt in a small quantity of water taken from the tank. Once it is completely dissolved, slowly add the solution to the to the tank.
For treatment and prevention of nitrite poisoning, measure out 3 teaspoon of salt for each gallon if water in the tank. Using a small container, dissolve the salt in a small quantity of water taken from the tank. Once it is completely dissolved, slowly add the solution to the to the tank.
When using bath treatments, weekly water changes of 25% should begin one week after initial treatment. Do not add additional salt once bath treatments have begun.
Similar Threads 
Besides, we can't be repeating most instructions so this deserves to be stick.
Epsom salt vs aquarium salt 
