Hi,
As far as I have been able to determine turning lights on and off does absolutely nothing to prevent or reduce algae, and in fact, it may actually do just the opposite. Algae respond much more quickly to short term changes in the environment.
I would suggest you leave your lights on for the duration of the photoperiod and perhaps only vary the intensity during the day by first some lights for a few hours, all for a few more and then the reverse near the end of the day.
Plants do best if the optimum level of CO2 is available as soon as the lights go on and in the afternoon they start to reduce their uptake. You can accomplish this by turning on the gas an hour or so before lights on and turning off the gas a few hours before lights off. This reduces your gas consumption, allows you to drive the CO2 levels to slightly higher values and it also gives your fish a break.
Cheers,