I have two 54 watt 10,000K T5HOs overdriven slightly with a Workhorse ballast and 2 x 250 watt MH with magnetic ballasts and 14,000 K lamps. Used to run 4 x T5HO with a mix of 10,000K and actinic. I no longer bother with any actinic lighting since it seems to be mostly for looks and does little for the inhabitants in my system, a few softies and LPS only.
I now run the two 10,000K T5s in the morning and evening. The MH cut in one at a time during the midday period, into the afternoon while the T5s are off. So MH only run a few hours.
Here's the breakdown.
2 x 54 watt T5HO - 08:00 to 11:00 and again from 15:30 to 19:00
MH1 - 11:00 to 14:30
MH2 - 12:00 to 15:30
There is a minute or two overlap between the T5 & MH lamps to ensure the tank doesn't go dark during the transition, so the timings above are rounded off to make it simpler to do the math for overall timing. So the MH are on only for about 4 and a half hours and both of them are on at the same time for only a couple of hours. The T5s do the rest of the work for 6 and a half hours.
I've found this to work well with my system but can't really advise what's best for yours. That will be a matter of personal preference and experimentation I reckon.
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