well if you intend to make a seperate tank for brackish then go right ahead.... but the addition of salt to your current tank will kill your other fishes. but if you are planning on buying a new seperate tank for brackish fish try posting in the brackish section for stocking ideas.... otherwise making your current tank brackish is a big no-no. Try reading the pinned articles in the brackish section and on google. this should help clear up a few things.