I've seen one of these homemade filters before, but I'm not sure what I'd need, other than the 5gal bucket. This really is for my dad. We have an outdoor pond in the area of 500 gals, layed out with PVC liner. There is some sand, rocks, and lilly pads in the pond itself. This pond is about 4 yrs old. There are probably about 6-7 fish in there right now. A white heron got the rest we had. There are a few comet goldfish, I think 1-2 fancytails, and one black moore. Currently, there isn't a filter on the pond, so thats' why I'm asking about what I'd need to make a decent homemade filter. List the things I'll probably need, and possibly their costs. BTW, we don't have plenty money, but would like to try to create something halfway decent for the fish. Just let me know what would be the best bet for my situation, Thanx in advance.