Want to convert your freshwater aquarium to a marine setup? The transition my be easier than you think. The tank that you already have will be sufficient for a marine aquarium, provided you didn’t dose copper or other heavy medications while you ran it as a freshwater tank. From there, just get rid of all the freshwater equipment (gravel, filters, etc) and start buying hardware for saltwater. You can drill the tank so that you can use an overflow box, or you could simply use a hang-on style overflow (which isn’t our first choice). Add a sump, protein skimmer, and a return pump, and you’ve got the basic requirements of a marine aquarium. Toss in live rock and live sand, fill the tank with saltwater, and there you have it. If you want to make things just a little easier, but unfortunately a little more expensive, just buy a reef ready aquarium and stand, that way you don’t have to rely on a hang-on overflow.