A special polymer bead made from a particular formula to be neutrally buoyant, porous and of size and shape to allow the maximum empty space between them. The combination of these factors creates a spherule that allows nitrate laden water to slowly saturate the Nitrastrate particles. The anaerobic bacteria within the bead consume the nitrates to create compounds which, when they emerge, oxidize and release harmless Nitrogen gas.Nitrastrate completes the nitrogen cycle.The first truly new filter material that lasts forever & improves with age.Use for fish, turtles and all aquatic species for a stable, pristine, naturally healthy environment. Blue 250 ct