So I've had my 20 gal marine tank for about 3 years and been successful with a hang on the back setup. Just bought a 60 gal cube and i'm going to try to turn my 20 gal into a refugium beneath it and do some plumbing (including drilling my new glass tank which i'm more than a little nervous about). Any advice for someone who's not done this before? Are skimmers required? if so, can anyone recommend a good brand or model?