EcoBio-Block Aquarium Stone for Natural Water Clarification and Odor Removal Featuring Beneficial Bacteria (Medium)Brand: EcoBio Block Color: Coral Features: ALL NATURAL TANK CLEANLINESS SOLUTION The Eco Bio Stone is a volcanic rock containing beneficial bacteria colonies, which are dispersed about every 30 minutes. Clarifies cloudy water over the lifetime of the stone, up to two years. AQUARIUM BIOLOGY WORKS FOR YOU Speeds up nitrogen cycle, with 100% pure bacteria in spores which germinate in early, middle and late stages, only germinating in the presence of