After searching for a few hrs last night I also noticed that MD also sells a jbj ocean series thats actually made for the Duo. At $30 a piece they all are in the same rough price range. Looks like evo nano might be the way to go. What about the tunze nanostream 6015? I see the PH on Tunzes site, but I dont see it for sale anywhere? I can find the 6025, but no 6025's for sale??