These Nubios Cut-to-Fit Phosphate Removing Pads have been specially infused with phosphate-absorbing particles to remove harmful phosphates from your aquarium or pond water. High levels of PO4 may cause rapid growth of undesirable algae and inhibits calcification by corals & coralline algae in saltwater aquariums. Like all Nubios infused media pads, this long-lasting poly-fiber material is up to twice as thick and is much more rigid than competing pads, enabling them to fit tighter, hold their shape longer, filter more effectively, and last longer.