Completely inert-- wont affect water chemistry Stabilized microbial sewage treatment technology Ultra-high surface area for enhanced filtration Just 1 Bio-Block piece can replace up to 20lbs of live rock Rapidly colonized by beneficial bacteria Stable ceramic base that will not decompose over time For freshwater and marine aquariums Maxspect's Nano-Tech Bio-Block are created using stabilized microbial sewage treatment technology with Biological Aerated Filter (W-BAF). This proprietary technology is formed into inert ceramic blocks which can be placed directly into your sump or filter compartment for aquarium filtration. Each block has an ultra-high surface area of 11,635 square feet, providing ample room for colonization by beneficial bacteria strains that can work to lower nitrites, nitrates, and ammonia naturally.