The photo "Tank before" shows stints which formed because of ejecting water by circulation pump. It was necessary to flow water for sea anemones. I tried sponge and a plastic knife before. The stints did not remove.
The polisher was not effective. I could not get #1500 or #2000 at a shop. The photo "Tank after" shows the result of using #1200. Water proof sandpaper is the best way to recover transparency of aquarium tank.