I have two such small pools and one large one. I keep fish in them and in summer, my alligator snapping turtle lives in the large one. I couldn't afford the water bill if I used city water, so fill them from the irrigation ditch. They were designed for a pump and filter but I use a gravity fed system & one way (downstream) flow thru. The ponds are 36 years old and just this past winter the drain pipe of the large pool froze and cracked. This has never happened before and I'm not sure how to fix it. All my fish died as the water leaked out below the ice. So this year, for the first time, I may not have my big outdoor aquarium. Mac Snap may have to stay indoors all summer.