HBH Aquarium Products Phosphate Filter Pad Cut To Fit 10" X 18" are impregnated with special phosphate-absorbing particles to pull phosphates from aquarium water. The use of phosphate filter media will reduce the need for frequent water changes & reduce the need for many other mechanical filter applications.This is for 1 Pad - 10" x 18"Designed to be cut to fit almost any filter application, including power filters, pond filters, trickle filters, wet/dry filters, drip trays, canister filters, powerhead attachments, and many other mechanical filter applications.Each cut-to-fit Phosphate Filter Pad is made of a long-lasting, durable polyfiber material perfect for aquarium use. For freshwater and marine aquariums.