I use Morton Hay and Feed salt, I use to buy the expensive stuff but I was on a tour of a public aquarium in Denver just before it opened and saw them making their salt water with it, I asked the guy if that was normal and he said most big aquariums that dont have access to natural salt water use it. I have never had a problem with it and 6 bucks for a 50# sack sure beats the alternatives, I do toss in a trace element/mineral block ever now and then.