Just a thought here, I added another power head to blast behind my rock and what do you know! POOP every where!!!! I mean it was just blowing all over my tank took 4 hours to clear up a little! So thought here is "tell me if i am wrong". blowing this junk up and allowing it to be picked up in to the over flow and into my skimmer would this possibly help lower Nitrates since it is not sitting in the sand? I did not test last night for I am setting up to do another BIG water change 50gal. This might be the end of my problems or a beginning of another. Now i have two return line and 3 power heads. Maybe i should look into setting up my return line better after all I do have a 1500gph pump running the show!