Check the listing for details. Hollow Bacteria Balls Filter Media. Condition: New. Listed at 24.99 USD. Hollow Bacteria Balls Filter Media 3L/1.5kg/ 3.3 lbs Condition is New. Each box includes mesh bag. Shipped with USPS Priority Mail. The anaerobic layer inside the filter media is suitable for anaerobic bacteria’s growth and breed. It can decompose the harmful substances such as nitrites through denitrification Biochemical ball have a highly permeable pore structure, plenty of aerobic space is suitable for the growth of aerobic nitrifying bacteria and promotes nitrification. Made of non toxic various mineral which through high sintering. Comply with ROHS after testing, better to protect the health of fishes. Acid and alkali proof and salt resistance. Effective filter all kinds of residues in water for a long time, effective in variety of filtering systems.