Try arranging power heads and or returns to increase flow at lower portion of tank. Even if some sand is moved around it will be okay and really clean up your sand. Also I find keeping nassarius and super tongan snails will turn over the sand and help. I also keep serpent stars which help the cleaning process. Another suggestion is to order a "detrivore kit". My sand bed has thousands of the microstars, various smaill worms, and who knows what else now. Yes some things do come in on live rock pieces and transfer to your sand bed, but with stuff feeding on them their populations don't get large enough fast enough to help. Just some thoughts and suggestions from what I have tried.