Fluval Clear X Filter Pillow (4 ct) – A pack of four chemical filter pads (“pillow” style) filled with special resins to remove pollutants. Fluval Clear X is formulated to eliminate impurities like phosphates, nitrites, and nitrates, helping to combat algae and improve water clarity. Each filter pillow fits in most filter types and rapidly adsorbs toxins, providing polished, crystal-clear water and a healthier environment for aquarium inhabitants.