Yeah I was afraid of an answer like this....
Afraid of what? The algae your getting is just not the photoperiod, like somewhatshocked said its all about the balance co2, ferts, and the amount of light. If the lights too high you will have algae no matter the photoperiod, if the co2 is going without sufficient ferts then you will only get algae.
How about giving more details about your exact light, fert regimen and co2?
Me personally, I only do 8 hours a day. If I do 9 I start getting algae. You kind of have to mess around with it for a while.