It has added prebiotics that made life so much easier to cycle new aquariums. It is our highly penetrable filter media substrate designed to remove ammonia, and nitrite and reduce nitrate in freshwater, marine, and reef aquarium. Through micro-bacterial activities, prebiotics can modify toxins into less toxic waste or even neutralize them completely by absorbing the toxins into your fish. Prebiotics are amazing! They will help your fish feel better, and keep your water clean.