The aquanique Universal Pump Filter Box provides pond owners with mechanical and biological filtration for ponds that hold up to 500 gallons of water. This filter box can also be used to house and protect your pump from damaging debris. This box comes with one coarse filter pad, which catches large unwanted debris in your pond water and one fine filter pad to catch smaller debris particles. Additionally, this pump filter box includes 10 bio-balls which promote the growth of beneficial bacteria. These beneficial microbes help eliminate harmful bacteria and organic waste, which lead to green water and foul odors. Recommended for ponds that hold up to 500 gal of water, Includes coarse filter pad, fine filter pad and 10 bio balls.