you should try to mimic the natural day, by keeping the daylights on at least 8 hours. what i would do is run the blues for 12 hours, and the daylights for 8, starting them 2 hours after the blues, and ending 2 hours before they go off.
kind of a dawn/dusk simulation.
as far as the algae, like you said, a good razor blade will take care of that fairly easily.
algae needs nutrients to thrive. if you are seeing more than usual, you might need to do a few water changes with good source water (R.O.D.I.).
btw, i also would look into changing out the stock lamps in that fixture for high end ones. you will be surprised how much of a difference they will make.
i suggest ATI aquablue special and ATI blue plus.