Jason,

I cant help much here. I manage lakes but dont build them. find lakedoc on an old post and drop him an email. he seems to know his stuff when it comes to construction. also Mike Robinson has posted some great info about marginal plants .

I have seen some small ponds/wetlands like you are describing and all have worked very well for filtering unwanted nutrients. I once did some water testing at a waste water treatment plant and those guys had what I can best describe as a floating barge of water plants in the waste logoons to help reduce nutrients. So I think you are on the right track.