A: Substrate in a Salt water tank is very important, it acts as a pH buffer and helps maintain the higher levels needed for the fish. You should use a Carbonate substrate designed for salt water use which should be clearly marked on the bag, one brand is "Florida Crushed Coral." The use of Coral in a fish only tank is purely for decoration and there are many plastic resin copies out there that look great. A protein skimmer is an option in a Fish only tank and a must have in one of the mini reef tanks where you keep "live" Corals and other animals. A fresh water bath is a tricky procedure that does remove many parasites, but should be taken carefully for a novice, a quarantine tank is a much better idea.