I only have a 70ish gallon pond, but I got one of these Python Pond Ulti-Vac and it works great. I could see it working in a much larger pond as long as it would reach the bottom (you can see the size in the link below) One of the reviews I read said it wouldn't pick up small stones, but it does for me, it picks up even 2 inch river rocks. It's not an insanely fast suction, although fairly strong, so you wouldn't have to worry too much if you had fish. I picked up some tadpoles (found them in the canister when I was done) and they were fine.. But, yeah, it picks up dirt, leaves, grass, etc... just great. (And you don't have to plug it in to an outlet, yay, you just attach the garden hose to one end and it creates the suction.) I've been really happy with it.