I have ALWAYS had freshwater fish, but my husband and I were looking at saltwater fish this weekend. I would like to put our current fish into a fresh water tank in my daughters room and convert our (currently freshwater) aquarium into a saltwater tank. Can you use a previously freshwater tank for a saltwater tank? If so, is it tough to keep maintained? What all do you have to do for a saltwater tank? Any advice would be appreciated. Thanks in advance.