Yep I use It (well i use Mineral Mud but its the same type of thing only a different brand name).
Great stuff, totally natural type of filtration andi highly recomend it if you have a sump.
You simply place this in the sump along with macro algea (or Mangroves) and allow the algeas to extract the nutrients. Works very well indeed. My MM system has been running since May this year and I have not even done a water change o this tank yet (although I am going to do a water change at the end of september)