These black plastic Bio-Balls provide a durable, versatile filter media solution for a variety of pond and water filtration systems. Their unique open design promotes water flow through the media while providing surface area for beneficial bacteria to colonize, supporting biological filtration and helping maintain healthy pond water. Unlike softer filter media that can compact over time, Bio-Balls maintain their shape to help minimize water channeling and encourage consistent flow through the filter. Use them loose in compatible filtration systems or place them in mesh bags for convenient removal, cleaning, and maintenance. Available in 1/3, 1, and 4.5 cubic foot boxes to accommodate a range of filtration needs.