Thanks for the info everyone. DT, the experiments are only run for 1 hour so algae isn't the problem. The lights are 8 cm below the bottom of the trays and heat is already a problem, so we can't really move them any closer. The water runs through two circulating chillers and they really have a tough time keeping the water cool, especially in the summer when the air temps are high, and now, when the water temp that we need to match is very low; we just ran an experiment where we had to get the incubators to 2.7 C, imagine that and 8 cm over 6 250 watt MHs!! Lots of ice and ice packs, and pretty heavy duty (ie very expensive) chillers.
Not sure what Kelvin the bulbs are as they don't say and neither do the boxes. They are 250 watt Philips single end screw in bulbs. I will check on the ballasts as well but they appear to be OK; the bulbs come on pretty quick.
DragonForce, what do you mean by a week? 24 hrs a day for a week? or 7 days of "fishtank hours", ie ~10 hrs a day for a week. I'd be very leary of leaving these things on while there is no one here at night and we don't have more than two weeks where we don't need the lights until next fall!
here are some pics and descriptions:
The lights in the lab are off because ironically despite how bright the lights in the incubators are the samples need to be in the dark at all times when they are not in the incubators.
First pic is a back view of the three incubators. Each has two trays, with a MH underneath. The two chillers are at either end. All the right hand trays connect to the right hand chiller, and the left trays to the left chiller. We need to be able to set the trays at different temps, hence the weird plumbing.
Here is a closeup of the MHs from the front. They are very close to the underside of the trays. The metal shields keep light from one MH from spilling over to the next tray.
Here is a close up of one of the trays. Each one has 60 slots for sample vials, and a lid when the vials are in there.
Another closeup of a tray, showing the screening to create a light gradient. We have a list of the expected light intensities for each slot (they are labeled A-F across the columns and 1-10 on the rows, putting the vials in is like a weird game of battleship!) so each vial gets a specific light intensity. Every sample gets 18 vials, 16 in a gradient and 2 dark vials.
A view of the incubators from the front. Some poor person has to sit in front of these things and measure the light in every one of those slots with a light meter.....and try not to get blinded every time they look into the trays....sunglasses are a necessity, which looks pretty weird when you're sitting there inside with sunglasses on! If you forget to not look in when you open the trays you see rows of green dots for about 5 minutes after!