Keep your River Reef aquarium in sparkling condition by staying on top of your filter care. Black carbon foam acts as a chemical filter, removing nasties from your aquarium such as heavy metals, chlorine, unwanted treatments and odours. Replace your carbon filters every 8 weeks. The Super Fine Filter Pads remove even the smallest unwanted particles from the water such as dust or scraps of uneaten food. Replace them every 2 - 4 weeks for sparkling clean water.