There was recently a poll done by another poster here and it seemed like people were all over the Board. 7-10 does sound a bit long to me. I'd recommend something more like 11 a.m. to 9 p.m. or something like that.
Keep in mind, though, that algae is not necessarily a bad thing (it means you're sustaining life) and also is food for the clean-up crew and some fish.