could someone please tell me what is the best length of time to leave my MH lights and acitinic lights on? I currently leave acitinic on for about 12hrs and MH for 6hrs

I keep my MH on for 7-7 1/2 hours a day.

thanks i will up mine a little bit

If you are trying to closely replicate the natural lighting environment as the fish / coral are used to in the wild remember that around the equator there is about 12 hours of daylight with 8-9 hours of intense sunlight.

I run actinics for 12 hours a day and my daylights for around 10. This schedule can be increased / decreased as the corals react. Longer lighting periods generally = more growth. Just remember to adjust lighting schedules slowly to give the tank time to adjust.