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.

Hi Metamog,

I have started seeds under lights... fero's and mam's... I used a flouro strip (48") with 2 warm whites and switched one to cool white. I have a timer to keep the lights on about 16 hours a day. I used no reflectors and my cacti have colored up dark and have stayed small and round. I had germination in about 4-5 days and some continued till about 2 weeks later. Just keep the soil moist early on. I sprayed with a dilute fungicide when I thought the moisture left the soil. They need heat and moisture more than light... once the cactus emerges from the cotyledons, then light becomes more important and moisture less important. hope this helps... I'm sure your little ones will do well.

Thanks you for your help!

shrubs_n_bulbs: Did your seedlings become elongated and light green, or how did you notice that you needed more light? (I spread the seeds on top of the soil).

Morgan,
I grow my seed and then the seedlings on shelves in a warm room in my house under twin 40w florescent tubes (both cool white) and sometimes with heat mats. Humidity domes are put on top of the flats and left alone until the majority are germinated and then for up to several weeks to months depending on the seedlings requirements. Depending on the plant and age of seed, I can get upto 100% germination. Take a look at my light setups and some of my seedlings.
Dan Rhoads
Lincoln, NE USDA 5
Light Cabinets
http://community.webshots.com/album/203201671EKClcI

Here is a link that might be useful: Some of my seedlings

Thank's for your information Dan, I've checked your nice gallery at webshots. It's really interesting!

Some of my Trichocereus candicans germinated today!!!!

That's right. Play it by eye and increase the light if the plants tell you to :)

I didn't let the seedlings etiolate (not much anyway, a few Lithops got a bit tall), but some looked a little pale. I had a mix of species and I increased the light to where the Gymnocalycium started to colour up. After about four months they all came out into the sun.