I just got a canister filter for a great price. I was wondering what media should be used in it? It has 4 trays in it. It also pushes out 325 gph. I have 25 lbs of live rock and 30 lbs of live sand in my tank now. It is a 20 gallon long tank. Thanks in advance. I would like to have some corals in my tank soon. I also have a skimmer that will be installed tomorrow. It is a Current USA nano skimmer. The skimmer is rated for 30 gallons. The lights are Current USA power compact 2x65 watts. Right now the inhabitants are 4 turbo snails, 8 hermits, 2 percula clowns, a sebae anemone, and a chocolate chip starfish which will be traded in for store credit due to the fact that the starfish isnt reef safe. Thanks in advance for any help.