Thanks! It's a bog filter or wetland filter made from a poly stock tank. A submersible pond pump in the deep end pumps to a manifold of slotted pipe in the bottom of the bog filter, it then flows up through the pea gravel and gravity flows/siphons back to the pool. This is how I built it: texasecofarms.com/pool-to-pond-the-bog-filter #grownostr