You use regular Epsom Salt from the pharmacy. If you have just a 1 gallon tank, just 1 teaspoon, 2 gallons equals 2 teaspoons and so on. Make sure the ES is 100%, no additives, scent or dyes used. Then take a small cup or other container, fill with a little tank water and measure the salt into that. Salt, regardless of the type, will burn your fish if you add it straight to the water because it makes heat when it dissolves. So dissolve it in the container first and add a teaspoon of the salted water to his tank every 10-15 minutes or so until it's all in. Leave it in for a few day's.