I salt all my fresh water tank, Just dont over do it. I usually stick to 1 tablespoon for every 5 gallons, but normally I short it a few just to be sure. After I was first put on to salting, and seen its benifits I wound never not salt my FW tanks. Im not a professional on the subject matter, but what I DO know is that my fish have never been healthier and looked better. I believe salting helps fight desease, speeds up there healing process, and helps maintain there slime coat. I dont know about salting with cats, but I prob wouldnt salt with tetras.