See, it sounds kind of gross (though ducks habitually swim in water filled with their own crap), but no one has so much as peed in this thing for probably two or three months. We still flush it every week or so, but no poop, no piss, no chemicals. You could probably drink out of it if you...
Well, to be fair, ducks actually are pretty useful for gardening (natural fertilizer produces plus they eat bugs and slugs) - as long as whatever you're trying to grow is outside their "snarf range."
As far as keeping the pool water clean, maybe someone else here has an idea, but I figure it's...