Helped to tear down a system like this. water dropped from above into a large tuperware container full of LR with an eggcrated supported blue pad filter. From there it dropped into a storage container of water (DT was a 65, storage container was a 30 gallon plastic drum. From storage container #1 one, it went into storage container #2, another 30 gallon drum. From storage container #2 it went into a small sump (probably 20 gallons) was skimmed, and an external Reef Dart pump pumped it back to the main floor. Pretty sweat set-up and obviously expanded his water capacity significantly. Down side, lots of salt creep, noisy pumps, and system has to be set-up correctly on when it shuts down everything drains into the 20 gallon sump and you got a major mess.