T describes the thickness of a fluorescent tube in eights of an inch. T12 is 12/8" or about 1.5". They are suitable although the most modern fittings tend to use T8.

Each timer is only driving about 60W and I'm sure they are rated for much higher than that. Shouldn't be a problem with safety.

Assuming a standard 20"x10" tray, you are providing about 40W/square foot, which is potentially more than enough. It is certainly enough for seedlings when positioned at 1.5". I would imagine that the three fixtures are actually slightly larger than the trays? If so, you might be better using just two fixtures with white side pieces to reflect some of the light back onto the plants.

shrubs n bulbs is right, you're doing fine. This is the right way to start out and to proceed. There is just no reason to buy all the fancy gimmicks on the market. I'm starting over 100 plants under two 4-foot fluorescent bulbs on one timer, and they're getting 14 hours of light a day, plus whatever comes in the window (not much extra with all this rain).

How many hours are you giving them? Fluoros are cheap - pour it on.

Yeah-I use fluorescents too-works great-used to buy those "plant lights" but they burned out so fast. I just leave them on all the time-water water water though. I usually start 100 + every spring. My Thunbergia is going insane as are my giant pumpkins(-:

Right is what works for U!

I too use 2 shop lights for a total of 4 - 40W floro's on a 2x4 foot shelf. I also use the cheapest cool whites I can find, run them 24/7 and replace them once a year. The bottom of the lights are positioned 16 inches above the shelf. After years of doing a little bit of everything with lights that is my optimum height. IF I want to put something closer to the lights I just use inverted plastic pots under them.

I have also found then 4 inch pots in gallon plastic bags with a tie make great mini greenhouses for seed starting and have started thousands that way. I open the bag when the seedlings hit the top of the bag (and u can reuse them over and over again.)

(frugal) John :)

don't run 24/7 with the lights. 16 hours is the max a lot of plants can take. Just like humans, plants need rest, or they literally grow to death.