[Lam Nguyen]

I am in the process of upgrading the filtration system of my outdoor pond and would like some ideas. It is a ~7,500 gal pond with two 3" Tetra BDs, two no niche skimmers, and two TPRs. The shape is oval and the dimensions are 21' L x 12' W x 5.5' D. I have two Nexus 300, one for each BD. These two Nexuses (?) will be pump fed by two Artesian PP 1/4HP. Each has a maximum FR of 4,100 gph, so after friction loss, I suspect that it will pump about 3,700 gph, which is the maximum FR that each Nexus 300 can handle. This will also give me a pond turnover rate of once an hour. The two Nexuses will be pump fed because they will be sitting above pond level and will gravity flow back either via a water fall or straight back to the pond. I will also max out on the K1 that these Nexus can handle. My goal is to grow about 7-10 koi.

The problem that I have and need help with is the two no niche skimmers. There are so many filtration ideas and I want to make sure that I design a circulation system that will complement the two Nexuses. I also want this circulation system to return back to the pond via the two TPRs to get some current. These are the options that I have so far:

1. No filtration needed. All I have to do is have a pump that pumps the water from the pond via the two no niche skimmers and return them directly back to the pond via the two TPRs. The rationale behind this is that there is already enough filtratin from the two Nexuses.

2. I already have a ~300 gal fiberglass chamber that I used as a mechanical vortex. I was thinking of having the two no niche skimmers gravity feed this vortex, fill the vortex up with a Jmat cartridge, and have a pump that will pump the water back to the pond via the two TPRs. However, my concern is the two no niche skimmers will not gravity feed fast enough since they only have 1.5" pipes and I want to pull about 3,000-4,000 gph.

3. Pump feed an Ultima II 4,000 from the two no niche skimmers and have it return via the two TPRs. I kinda like this idea.

4. Scratch the return via TPRs and pump feed two fiberglass filter boxes filled with either Jmats or Jbrushes and return via gravity. The only concern here is I really need current for the pond.

One more question for all you KB gurus out there: I am thinking of putting a couple of retrofit aerated BD domes in my two already-existing Tetra BDs. Do you guys think that this is necessary since the water returning from the two Nexuses will already be aerated? Any help is much appreciated. Thanks in advance, guys.