ZooBest Bio-Whirls A are a high performance filter medium for fresh and marine water aquaria. The high performance bio whirls ensure a rational, natural water filtering. The water is returned again and again when flowing through the special lattice structure and swirled turbolent. By the centrifugal energy occuring here the dirt particles become filtered from the water. The special lattice structure from the ZooBest Bio-Whirls offers a maximum surface, on that itself a biological film can form.Do you have questions about this article ?