Aquascape BioBalls Biological Filter Media are an ideal choice for biological filtration. Each ball provides 19 sq. in. of surface area which beneficial bacteria can colonize, while its paddlewheel design helps to de-gas the water and maximize oxygen levels. The center channel allows the balls to be strung together for quick and easy cleaning. Plus, the BioBalls won't break down like traditional media, offering years of reliable use. Compact design and media net with drawstring make installation simple.