Designed for the JBJ Nano Cube aquarium filter and other filters requiring a sponge block. The nano cubesponge design provides mechanical filtering of solid waste matter from your aquarium water. This will also prevent early clogging of other filter media in the filter path. Sponge Filter Media should be replaced every 2 months. Alternate the replacement of the Sponge Filter Media with Activated Carbon Media to maintain biological filtration.