Why don't you reduce the number of lights you're planning on and buy CFLs in the 80-100W range? THese lights are spectacularly bright, cover large areas, and overall, will probably cost you less.

From topbulb.com:

8 55W CFL(440W total) @ 18.95/ea= 151.60
5 85W(425W total) CFL( @ $26.95/ea= 134.75
4 105W(420W total) CFL @ $29.95/ea= 119.80

Truly, less is more. Less bulky, less complicated, less hard to manage with timers and wiring.

Sam

Thanx 4 the advice but too late here because all the lights have been purchased. What's my best option with what I have?

Question re-phrase: How many watts (or lumens) do I need over a terrerium/orchidarium that's 5 feet wide, 3 feet tall, and 2 1/2 feet deep (about 38 cubic feet)? Thanks!

I guess the answer is "as many as you can possibly use without damaging your plants". It depends on your cooling scheme, plants, moisture, Etc.

Can you return the bulbs? For a terrarium, I'd be worried about heat buildup with 8 bulbs. My terrarium/orchidarium is 4'x3'x2' and I have 2 80W CFLs over it. They are very bright. 2 or 3 80-100W bulbs would probably be more than enough unless you have extremely light-tolerant plants and you can keep the heat down.

Sam

8 should be just fine. They definitely will not be too much. *Might* end up being not enough, but it depends on which orchids you put in there, and how close you mount them to the lights. It's next to impossible to leaf burn plants with fluo's unless the leaves/flowers actually touch the bulbs, so don't worry about that. Just see how it goes. If the leaves are growing nice and compact, not stretching out and getting pale in colour, and if variegated leaves are keeping their colour/variegation, then you have enough light. Some leaves will get a purple tinge the indicates plenty of light (but not too much). I think you'll be just fine. BTW, what kind of bulbs are they? Cool white? Daylight? If either one of those, then they'll be good.

There will be 4 6700 K and 4 5500 K - all are compact flo's, meaning they produce 4-6 times greater light per watt.

I think you'll be just fine. They sound good!

My two cents worth is that I used 4-foot fluorescent tubes in a "shop-light" fixture. This is really really cheep and available anywhere. $1.50 per tube and $10 to $25 for a two or three tube fixture. I have 80 watts (two tubes) over my terrarium 4-foot long and narrow and 2-foot tall. This is really minimal. Only low-light plants will bloom here. I might change to a 3-tube arrangement (120 watts). One problem with really cheep fixtures in the $10 range is that they make a little humming noise, even if they say "quite" and "solid state balast". I agree that sun-loving plants can grow one inch from the tube with no harm.

You might just want to add another shoplight fixture over your terrarium. When I used tubes, I used 2 2 bulb fixtures. Still, the light is minimal at best, and that's why I switched to the HO CFL bulbs.

Sam

You're saying that I should add additional light on top of 440 watts of HO CFL?

Woops, I was referring to cdfortin, right above my reply. I wish this forum software made it easier to quote people...

I've already told you that I think you have more than enough light, just that I would have gone about it a bit differently.

Sam

Blowing it even more, I was referring to dfourer, not cdfortin...