The algae cleaning magnet is comprised of two magnetic assemblies, one goes inside the aquarium wall and one on the outside (so they magnetically engage each other). The inner magnetic assembly has a scrubbing pad on it.
When you move the outer magnetic assembly (by hand) the inner assembly moves in tandem and scrubs the algae off.
A fun and easy way to remove algae from your aquarium with no messy cleanup after cleaning -- imagine that!
