CerMedia MarinePure Biofilter Media GEMS 

• Designed for Ammonia, Nitrite and Nitrate Removal
• Primarily designed to provide deep anaerobic zones for de-nitrification in passive systems.
• Live rock substitute-popular among reef hobbyists as a substitute for live rock because it reduces nitrates more efficiently without harming the environment.
• Use in sumps, stacked in extra-large filters.