GEO Cryptic Biological Reactor (CBR), loaded with MarinePure ceramic media balls. For those that don't know, a cryptic reactor is used for high-capacity nitrifying filtration. Water passes around and through the media, allowing the beneficial nitrifying bacteria that has colonized the media to reduce toxic ammonia and nitrites to near zero. It also reduces phosphates significantly and dissolved organics. The vinyl wrap keeps the media in total darkness to prevent algae and encourage fauna that thrives in the dark spaces in the natural reef.