dont the seeds need light to know which way to grow when their germinating?

once germinated, is the light used as a source of heat ie standard globe or does uv come into play. i use the mercury vapour bulbs for my snake, thinking theyd be pretty full on for seedlings though?

god, i hope you don't use mecury vapour bulbs over night for your snake - the poor thing will wish it was blind :p

I used to use mecury vapour bulbs and fans to grow tomato plants 4 or 5 times quicker for experimentation purposes. You could literally watch them suck water up!

Yes, they'd be full on at close range for seedlings.

I'd suggest they're full on for a snake to!

only for daylight and heat, i have a pretty deep tank, and he still chooses to bask under the light which is about 40cm away from his basking spot. come to think of it, since ive been using these lights his probably grown 5 times as big. heas only 4 and he's nearly seven foot long!

Try it on some test seedlings, from what I got told about those lamps and cacti seedlings they will burn to a crisp

On the issue of light and seed germination. Water, warmth and oxygen are the only fundamental requiremetns for seed germination. With that being said there are plants that require at least "some" light to trigger the pre germination process.

With cacti seed I have found that light will trigger the pre germination development, it also accelerates germination as it occurs. I am of the firm belief that light is necessary to trigger germination many cacti seed and when light is utilised especially natural light a far greater germination % will be achieved.

As to which cacti rely on light to trigger germination I have no info on but would expect germintion to increase in many if not all species. As stated earlier I also believe natural light produces much better results.

I use a combination of cool white flouros and gro-lux flouros in equal amounts over my seedlings with very good results.