I am in the process of learning about Saltwater tank setups.. .i hope to have one set up in the near future. So far i have a 60 gallon hexagon tank with hood, and i have chosen the Fluval 306 canister filter. What is the deal with protein skimmers? i would rather not have the type that hangs on the back of the tank, but aside from that, i have no clue what to shop for. Advice?