The inner magnet is more than 3mm away from the aquarium and thus prevents the jamming of the aquarium sand. The two plastic blades remove the algae considerably better from the glass panes than a flat cleaning surface - almost as good as a sharp metal blade. The life of a blade is from several months up to approx. one year. The low flow resistance during the cleaning with a simultaneous high magnetic coupling, makes a separation of the magnet nearly impossible. The large blade should only be modified with the included stainless steel blade for aquarium glass panes with particularly tough algae, e.g. older deposits on the side walls or thick calcareous algae.