Maglife NitraStrate filter medium is a special polymer bead made from a particular formula to be almost neutrally buoyant and porous. The first truly new filter material improves with age and lasts forever. The size and shape of each particle allows the maximum empty space between them. The combination of these factors creates a spherule that allows nitrate laden water to slowly saturate the particles. The anaerobic bacteria within the bead consume the nitrates to create compounds which when they emerge, oxidize and release harmless nitrogen gas. It completes the nitrogen cycle. Forms a stable oxygenated environment between the particle collects and naturally processes all the debris of a fish tank. It is an ideal anaerobic de nitrifying environment. Anaerobic colonization occurs inside each particle and remains even when substrate is allowed to dry. Remains clean and never needs replacement. Use for fish, turtles and all aquatic species. Patents covering its many social features have been engineered into it over 7 years of research and development. Effective in fresh or salt water. Stabilizes even tiny systems. A 2 gallon marine fish setup is now possible and easy. Because it is almost neutrally buoyant, fish love to swim through it and hunt for food. It is uniquely beautiful and available in colors to match any decor. Now maintenance is so easy that anyone can do it, not just the avid hobbies. Available in yellow color. Includes 250 beads per pack.