Right now I've got an aqueon 55 and aquaclear 110 HOBs on it, but I'm getting an oscar soon, so as my stock grows I'll need to consider the bioload of some SDs, an Oscar, severum and a pleco, but the tank being glass, I can't drill overflows, so I don't know how I should go about pumping water in and out of the tank, any suggestions for other filtration methods or ways of pumping water?