Hi. I don't have any links to sumps, but they are really aren't complicated. All a sump is is a body of water located outside the tank (usually below) which holds equipment such as skimmers, heaters, etc. Water overflows from your tank (there are several ways this is accomplished) into the sump, then it is pumped back up via a return pump (can be either inline or submersible). That's really the gist of it all. A sump can be custom built, a ready-made aquarium, a bucket, a rubbermaid container, etc. .... so long as it holds the desired volume of water.