Here is THE BEST algae scraping tool you could ever buy (well, in my not-so-humble opinion, lol)

http://www.algaefree.com/easy_blade.html

I attached it to my Tiger Shark Float, and everything was cleaned off in just a few seconds - even the coralline!

I bought it at my LFS. With my discount, it was around $11 after tax... not bad at all!