You should run them a minimum of 10 hours per day. 12 is better. I run my lights here 12 hours. You can start the actinics about 30 minutes early if you want and let them run for 30 minutes after the white lights cut off. You don't have to do that, but some folks like to for the aesthetic effect...kind of like a sunrise/sunset.
One thing I should point out is that you'll only need 3 MH
bulbs on a 6' tank. Each MH
bulb will cover 2' of tank. Once you add the MH
, you can convert all your VHO
to actinic if you still have room for all of them. At that point, I'd either have them all come on at the same time or do the 30 minute sunrise/sunset thing. You can get dual and triple ballasts for MH
. I kind of like the singles as I think they would shed heat better. You might want to look into the electronic ballasts that are available for MH
now. The aren't as large as the core/coil ballasts and run much cooler. The manufacturers claim the bulbs will burn brighter and last longer on them as well...I'm not sure about that.