Our biological filter gravel and substrates provide naturally craggy, porous surfaces bacteria love to colonize. Larger biological filter gravel and substrates like volcanic rock are great for wet/dry filters and canister filters and some of ours are live for optimal bacterial growth; this media is large enough to withstand high pressure flow and can be rinsed and reused. Smaller substrates like sand should be reserved for low pressure applications. Place biological filter gravel and substrates into filter bags for easy maintenance.
