Each scraper comes with a set of three different blades: one thin stainless steel blade for regular algal films, one thick stainless steel blade for cutting through coralline algae, and one molded plastic blade specially designed for use on acrylic tanks. 

Sleek form factor allows you to clean between closely spaced rocks and aquarium glass.

The thick blades are for the removal of hard crusts or coralline algae from glass. The thin blades are for the swift removal of algal films and coralline.  The blades are held securely in place with two metal screws.