I've used BRS for my GFO and have used the regular in the granular and pellet form and also the high capacity. The high capacity will remove twice the amount of phosphate as the granular and pellet for the same volume, but I found that my sponges in the reactor clogged before the medium was exhausted. Because of that I like the regular GFO in the pellet form. The granular I found to be too fine to be practical so I stick with the pellets.