How do you filter a pond that is on the ground. You cant use a conventional wet/dry cuz the pond is on the ground. Or can you. Im just trying to get some insight on how to filter one of those 300gal rubbermaid ponds. Any ideas?
have this with an fx5 works well! I used rubbermaids for the filter too! First section is 2 prefilters, second is bioballs, then 3rd is those plastic sponge thing and then gathers in the 4th and spills back to the tank

This was the sort of thing I had over my tank water pumped up by pump flows through gravity takes it away had extra hole at to as emergency over flow if media got blocked. But if you are running with your idea you must have the hole drilled inside the tank, about a half-inch below the water level.That way, if your pump failed and a back-siphon occurred, you'd only lose as much water as was in the tank above the hole before the hole was exposed to the air, breaking the siphon. This is the way I had it set up in my tank and it works correctly every time you turn off the pump.