Lighting Question For Indoor Seedlings

im starting my garden a little early this year by planting my seeds indoors a few weeks before the last frost to get a jump on things this year....now i have a 20W Cool White flourescent tube that i got from walmart a long time ago cause it said grow light on it...lol...anyways...im just starting about 10 tomato seedlings, 10 Okra seedlings, and may even start about 4 zucchini plants a little early too....now would this light be enough to have over top of the flat of seedlings, or should i add a few CFL's to the picture....im not gonna allow them to get big in there or anything, just once the soil gets warm enough i want them to be at least a good few inches tall come plantin time....ive got them in a little grow room i had built, so all the light being put off is pretty well contained in the room...not too much wasted, just wasnt too sure if the light was strong enough to support all the seedlings....Any advice is greatly appreciated!!! oh ya and whats a good schedule too keep them on...i was thinking 18/6 is what i was gonna put them on, but what about straight 24 hours...could that be a bad thing??
Once again thanx for the help

thanx...thats what i was hoping you would say....i think 18/6 is the usuall lighting schedule during vegetative growth, so thats probobly what ill put em on....i know you can veg ganja under 24 hour light, so i was wondering if you could do the same for the vegetables....hopefully someones got some knowledge on that...thanx again yermom