My tank was custom made so they do not offer this that I have seen in "normal" tanks. Just think of it as a 24"x 24"x 10"(depth) tank molded directly onto my main tank. The " overflow teeth are slits routed into the acrylic between the main tank and the overflow tank. The overflow tank has 2-2" dorso stand pipes that I put around 2000 GPH through. There is no siphon to break etc. This setup works great because my tank is veiwable from 3 sides. The narrow end with the overflow sits into the wall. There are no obstructions it the tank at all. All my flow is controlled by cloosed loop/loc-line systems feeding the top and bottom of the tank. No powerheads, overflows, etc to clutter the tank.