lots of us scrape algae off the glass... it will just become like "dust" and float away to be filtered off or better still eaten by corals, pods or whatever...
If you want phosphate/nitrate removal you are better off using macro algae...
If you looking at scraping off, one of the favourite tools we reefers use is a credit card (expired of course!) or similar hard card.. I use a plastic ruler...
For more "hardcore" algae that has been "baked" onto the glass, you can try using a razor blade, just be careful of your fingers and the glass silicone...
If you have just a light coating of algae can buy a magnetic cleaner also.. i use that quite often, don't even have to get my hands wet...