I currently have a Fluval Studio 600 that I converted to a marine tank. It is 33 gallons and I built a sump out of a 10 gallon tank. I have approximately 30 lbs of rock (some live, some coral) and 40 lbs of live sand in my display tank. It is stocked with a lawn mower blenny, watchman goby, 3 blue green chromis, 2 ocellaris clowns, a keyhole angel, a bubble tip, 1 emerald crab, 8 hermits, and various snails. In my sump I have an intake sections that has a filter sock filled with charcoal pellets and filter floss, a skimmer section (no skimmer yet), bubble trap, fully lit refugium with 5 lbs of live sand and cheato, a partially lit refugium with 5 lbs of live sand and red garcialaria, and a return pump section. There is also a peppermint shrimp that refuses to stay in the main tank and has taken up permanent residence in the sump/refugium.