ZooBest Filterwool Biolen is a special filterwool for the mechanically and biologically cleaning of the water in aquariums or garden ponds. While the white filterwool has a fine structure, the green filter wool has a rougher structure for biological filtration. After a short period the ZooBest Biolen filterwool is a ideal substrate for important water cleaning bacteria. You can use this filterwool as a stand alone filter media or in combination with others. It can be placed in a external filter behind the filter rings or in a multi chamber filter. The ZooBest Filterwool Biolen can be use in freshwater, seawater and garden ponds. It is free of harmful substances and chemical neutral in the water. Made in Germany.the following box sizes are available:Bag with 100 gBag with 250 gBag with 500 gBag with 1000 gSack with 5000 g