This allows you to clean the algae off The within from the glass through the use of a magnet on the outside, so you don't have to set your hand in to the aquarium. You can expect to pay out a little bit more, however the advantage is worth it. https://leadingdiscountpetstoreua53196.laowaiblog.com/36497307/the-5-second-trick-for-beginner-aquarium-checklist