Review on 2-in-1 KEDSUM Magnetic Algae Scraper for Aquarium Tanks - Floating Fish Tank Glass Cleaner & Scrubber Brush with 2 Blades [Non-Slip, Scratch-Free, Magnetizing] by Luciano Filpo

My only regret is not buying it sooner. I am very happy with it. The magnet is so strong that it is difficult to separate, which is exactly what I wanted from this type of glass cleaning tool. The clean side is a durable Velcro-like material that cleans incredibly well, but the "bristles" are wide enough to prevent clogging. The outer glass side is also made of a soft yet durable material. I tested the interior for buoyancy and it floats right off the surface with no issues. I don't think this will be a problem as the magnet is so strong that you cannot easily pull them apart. But if you do, don't dive elbow-deep into the tank to pick up the other half. Just an all-around great product at a great price.