Bio ball made of advanced non-toxic PP plastic, processed into nets pore structure.Internal porous structure made for the adsorption of nitrifying bacteria,conducive to Oxygen convection exchange in oxidation, and provide large bio surface area for the reproductive growth of nitrifying bacteria.Inside with filter cotton, which can live more nitrifying bacteria, further improve the bio capacity of bio ball. Bio ball have different sizes,bio balls are with large area can provide growth space for nitrifying bacteria,to establish a complete and balanced biological filtration system.