Need Actinic Opinion

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I just added my two six foot actinic bulbs to my tank, there 12 inches above the water running along my halides. I get alot of nice natural sunlight through my two windows in the morning so i was wondering if i can run my actinics at night for two hours or can i run them for four? my halides are on 12-8, so i would run them 8-10, or can i run them 8-12? any opinions are appreciated. Also since they will only be on for such a short time do i have to "acclimate" and start running them for a little at a time?

Thanks in advance.