yea id stay away form that.... it doesnt say its safe to use on the INSIDE of a tank.... ANd the fact it says it has a "protective film that lasts for 6 months" says do not use this in a reef tankI was recommended this product to use on severely stained windows, from hard water, instead of replacement from a window company. They said that they use it all of the time to clean the water stains, I tried it and it really does work. I haven’t tried it on my tank yet, but it does state that it is aquarium safe. I get it through Amazon. It might be worth a shot.