minimum photoperiod

i was wondering if anyones tried to figure just how short of a photoperiod you can get away with? i'm running 2 150watt metal halides..one comes on at 12 and goes off at four.the other goes on at 2 and goes off at 6 i also run a standard aquarium light {40 watts i think} with an actinic bulb from 11 in the morning to 1 at night.basically just so i can see whats goin on after work{i work nights} i have had it like this for 2 weeks now and about a week in i noticed my frogspawn was staying semi open until the actinic went off. i'm pushing it as it is as far as watts pergallon goes{120g},but as far as photoperiod?

 

bump

 

they say anymore then 12 hours causes algae and doesn't help the corals. but using just some actinics probably wouldnt be bad for them. in the natural reefs many corals stay open at night and increase there zooxanthellae to take advantage of the moonlight. on too your question about the halides. the sun usually is at its peek for 6-8 hours, so i dont think your halides are pushing the minimum