Im looking at a system on ebay with a Thomas pump and have requested pricing minus their ring diffusers.

I want to build a couple of disc diffusers (thanks Bill Cody for the ideas/ pics) So I am looking at just buying four difusser heads, two for each system.

There are numerous places that sell the 9" discs but prices vary and I cant find a CFM rating?

are any of these discs better than the others?

http://shop.hoosierpondpros.com/Vertex-9-Single-Air-Diffuser-VertexDiff9.htm

http://www.aerationstore.com/product/DD03.html

http://www.aerationstore.com/product/DD01.html

http://www.airanchor.com/our-products.html