Sumps can get a bit $$ but If you have the time you probably could build one like me. It only ended up costing me about $250 for a full 10 gallon sump w/skimmer but if you buy it already built it can end up costing $300-$600. They arnt hard to set up . A sump is pritty much a small tank that holds all you equipment such as protien skimmer,heater, filter media, ext. It is mostly used to keep all the junk that you don't want showing underneath the tank. The biggest problem wqith sumps is over flowing.