+1 on rygh.... Also make sure the efluent from the biopellets is going to the skimmer, water change also helps. This is the reason why I switch to sulfur media, in my opinion its easier and less maintenance.
it could be calcium precipitation, check your magnessium level. Water change and adding carbon will help but it's always good to find the root cause.
http://reefkeeping.com/issues/2005-07/rhf/index.php