The Two Little Fishies AlgaEraser is an advanced 16" aquarium window cleaning razor. It includes two replaceable stainless steel metal blades for glass aquariums and a plastic blade for acrylic aquariums. The thick blades are for the removal of hard crusts or coralline algae from windows. The thin blades are for the swift removal of algal films. The blades are held securely in place with two metal screws.