This is filter media designed to allow the growth of nitrifying (and sometimes de-nitrifying) bacteria to remove nitrogenous wastes such as ammonia and nitrites. 

Bio filter media should ONLY be rinsed in used aquarium/pond water (then dispose of the water) or de-chlorinated tap water (non chlorinated well water is OK too).
Even then excessive rinsing can destroy some nitrifying bacteria, so do not worry about rinsing until the rinse water is perfectly clear.