Filter insert with activated carbon for JBL internal filters of the CristalProfi i range. Clean and healthy water: activated carbon insert prevents water discolouration and odours, removes medication residues. To use: simply position the filter cartridge in the filter container instead of the filter sponge. Water-neutral, high-quality activated carbon which does not release phosphate into your aquarium water. Renew after about 2-3 weeks or immediately after the problem has been solved. Does not release bound problem substances back into the aquarium water. Package contents: 1 ready-to-install filter insert with 190 ml high-quality activated carbon.