Hi all, I've got a question on sizing a filter for a small stock pond. I have 120 4-6in koi in a 1,000 gallon pond 10ftx4ftx3ft. I currently have 2 19in pool sand filters filled with lava rock but they can't keep up with the fish load. I was thinking of switching to a 55g drum filled with 2 cubic foot of sponge and 3.5 cubic foot of bio balls, would this be enough bio filter to keep up with the amount of fish? I'm limited on space, otherwise I'd go with a 3 barrel setup