I've recently set up a 30 gal tank with 10kg of live rock in for my filtration. I added marine colony to get things started and 2 Clown fish. Everything is going fine so far apart from 'scum' on top of my water, now I don't know if this is the colony or dust etc from my room. I've been told to get a canister filter to help but I'm liking the idea of a protein skimmer better, mostly due to they seem easier to maintain instead of a canister filter. Does anyone know of any good ones I could use for my tank size, I would like one that doesn't sit in the tank if possible so it doesn't take up any tank space. Help would be really appreciated. Thanks.