In the past, I've put a folded up newspaper over the ones who needed darkness. Some years I figure that darkness is acheived by being under the soil, so I don't worry. Most of my seedlings have been up for a couple of weeks and under lights. I still wake up in the am and see someone else has germinated over night in the dark and cooler temp. Good luck!

Recently began to think the amount of light is directly related to the required depth of planting the seed. See depth page 54 of the attached book. Here is a link that might be useful: Light/depth This post was edited by bugbite on Thu, Mar 28, 13 at 12:07

They will germinate fine under those lights. The Fluora spectrum has more red light than a cool white fluorescent (a lot less green) and a better spread of red light, but the light requirements for seed germination are very low (you didn't bury them an inch deep did you?). I don't think you'll notice much difference on the heat, unless perhaps the tube isn't well matched to the ballast. You might find that 2x18W is not quite enough for growing on the seedlings after the first few weeks. My propagator is a very similar size and I move up to a total of 50W when the seedlings are all up. Maybe you'll have more natural light by then. Think about replacing transparent parts of the box with something white or reflective. Light which you can see from outside the box is not helping the plants.

Should not be a problem. I move my plants out of the "greenhouse" with heating mats as soon as I see about 6-7 plants of the 9 cells in 8-09 inserts (8 breakaway sections with 9 cells each in a 1020 compatible flat. 72 cells total). The plants need to sleep at night in any case, so they will be very used to warmer temp during the day and colder during night. 60F might not be totally optimal, but I just don't think it is going to make a whole lot of difference in the end.