The Fluval Edge Foam & Biomax Renewal Kit is an excellent replacement kit for aquarists of all levels to have on hand. Inside， you'll find a handy foam pad and BioMax rings， specifically designed to help keep your tank cleaner and your aquarium life happier—whether you have finned friends， or underwater plants. First， the foam pad functions as a layer of mechanical filtration， working to trap and collect particles and debris from the water. Meanwhile， BioMax rings offer biological filtration. With a complex pore system， these rings encourage the growth of beneficial bacteria. The result is a healthier aquarium with less waste and clearer water.