I was contemplating something along these lines after I had to fix the float in my toilet tank. If I had overflow water from the tank trickling into something with a float valve in it could I then have it open up and "flush" water through a filter. Would siphoning action be enough to propel water through a filter and back into the tank? Im thinking that this would be feasible on a huge scale (i.e. roman aquaducts) involving long drops and massive pipes to small pipe conversion but nothing feasible for pond or aquarium. I know its a bizarre idea from a MFK newbie but Im braced for impact.