never had a thick algea on hood problem (yet) but I don't figure anything other then scraping is going to help. my "hood" is acctually two sheets of plexi I cut and hinged together (get shots of it later) and then I just laid the light on top of that (light is exactly the length of tank so ends sit on plastic and have about a .5-1cm gap between light and plexi but I'm thinking of getting legs for the light so it'll be suspended above tank and look more showy.
Phillip