Ya if it is in freshwater, start buy using freshwater aquarium salt so you can kill the ick quickly. Add 1 tablespoon for every 5 gallons and also raise the temperature a few degrees 2-3. And once it gets over the ick, usually in about a week or less if treated right, then start turning the tank into a brackish. You need to do this by adding marine aquarium salt and raise the specific gravity up by .02 per week until you reach the goal. Do a general internet search for brackish tank set-up and it should fill you in.--------------------once you get it over the ick this time and get the SG up to brackish they usually never get it again. The freshwater salt at the same dosage will help the other tank as well.