PMD presents as a ruffling at the edges of the mantle, as it progresses the ruffling is more noticeable, followed by diminished extension of the mantle. GFO=Granular Ferric Oxide, used to remove phosphates there by reducing algae. No scientifically documented relation to GFO and PM. It's thought that clams already infected may succumb to the disease at an increased rate. Match FW to displays water pH and temp for FW bath. Burp clam when returned to display by turning the clam upside down to dislodge trapped air bubbles.