Thanks Zep. I’ve actually been on quite the research journey with NSPs over the last few years. Originally I was planning to put an NSP “marsh” in the center of the donut, and use a pump to pull water from the top of the donut, into the marsh, and have it flow out at the bottom of the donut, where the water would then circulate back around each side of the donut to the beginning of the marsh again. My thinking was this would create filtration and horizontal flow.

As I researched it more it seemed that these marshes can get “clogged” quite quickly. I was also worried that the water circulating horizontally wouldn’t be enough to get oxygen to the mud/water interface at the bottom of the pond where it’s needed to decompose organics. So I decided to scrap the central marsh and use the pump in the middle of the donut to circulate the water horizontally (2000 gpm with a series of “air lift” pumps) and put the “marsh” around the outside of the pond where water would flow through it at the edges.

At this point I thought I should probably have bottom diffusers to circulate the water vertically as well. But if I’m going to have vertical circulation it seems that horizontal circulation is redundant.

So I’m coming full circle a bit. I’d like the water to be clear, maintenance to be minimal, and operation and construction costs to be minimal. A big wishlist for sure. Right now I’m thinking I have a series of bottom diffusers to create vertical circulation and leave it at that for now. But I’m not sure if that’s right or best.