There is a ad for a little fish tank that has a odd way of changing the water. You pure fresh water in and out comes dirty water. I was wondering if there was something like that for larger tanks, heck the thing seems to good to be true so does it even work at all ? Thanks for the advice so far.. but I am taking more about the cleaning device and not the small tank. I been a around here for a while I know better than that lol.