Hello I am new to the hobby. A friend of mine recently gave me her 30 gallon saltwater tank, it has a DSB some live rock two clown fish, 4 hermit crabs, a pink leather coral, and two nassarius snails. The tank also has a metal halide lite, a filter and a protein skimmer. I have had the tank for about a month. and have finally gotten all the water levels under control except for the nitrates which are around 20. Just to clarify that the tank came with all these inhabitants the tank has been establishes for 3 years before I got it. My question is I would like to make this into a small reef tank and keep only the existing clowns as fish but I am uncertain as to what would be compatible in a small tank such as this. Also how do I get the nitrates to come down so I can add new inhabitants. The tank was sorely neglected when I got it and it has not been easy getting the nitrites under control but I finally have.