guys, I use DE all the time... in my in-ground pool filter system. It's a DE type filter, it has a series of large nylon mesh type filters spanning a manifold and the DE powder is poured into the system usually via the skimmers around the sides of the pool and the DE powder coats the big filter grids (50 + sq. ft.) with a coating of DE and this acts as a super filter, it filters down to under a few microns, when it gets clogged you simply reverse the flow and backwash the crud and DE down the drain then recoat the filter with fresh DE to go another month or two. I never knew it had other capabilities.. I buy a box at Leslie's Pool Supply (a national pool service chain) it's 25lbs. and it's about $20 a box. Seems like I saw it at Walmart too, they had a small section for swimming pool supplies like chlorine tablets, shock, etc. and I think it was available in 5 or 10 lb packages.