I decided to splurge on my plants and I ordered this:

https://www.amazon.com/dp/B00GDEMD7U/

It will be here tomorrow. My plants are excited.

You are going to love this bright-light fixture, Carol. If you have been using the standard T12 or T8 fixtures, you will be amazed at the brightness of this fixture.

@drdawg I've only been using a few CFLs clipped onto a pole -- so I think you're right. My plants are starving. I'm going to put it right over my 4 shelf plant stand that's about 3' long - Not sure if it will do much for the plants the 2nd shelf down, hopefully. Eventually my new 6 x 8 HFGH will be joined with the existing HFGH 6 x 8 and husband is going to "raise the roof" (literally) - and then I hope to have a nice bright fluorscent in the ceiling (maybe T5).

All my T5 bubs(tubes) are HO, so I am not sure whether your tubes will produce the heat that mine do (I also have 4'x6 tube fixtures). Just be sure not to get your tubes within 6-8" of your plants until you know what the heat produced will be. Standard T12 and T8 fixtures product little heat and you can position those tubes within 2-3" of the plants without worry.

@drdawg good advice. It did say on Amazon that they are not hot - and they aren't HO. Hopefully they are still powerful enough to do some good. They had really good reviews.

I am quite sure, since you are not having to light a large area like I am, that T5 fixture will do well for you.

@drdawg I was going to mount these above a metal four shelf unit I have in my small 6 x8 GH. The reviews said it runs cool enough to put it within 6-8 inches of the plants. Do you think it is powerful enough to provide light for the whole GH if I ceiling mount? It is only 2' x 12 inches deep, four bulbs,x 24 watts each, and total 8000 lumens. Maybe it's just big enough for that one side of the GH?

Clearly I don't know what I'm doing here ...again my inexperience shines thru. haha.

UPDATE. googling and a garden shop that sells similar had a chart and for the 2 foot long 4 bulb it said to place it 6 inches to 2 feet from the plant. So I guess that answers the question.

Carol, I don't have any 2' fixtures, but here is what I have in my "Orchids Only" greenhouse. I have two, 4' x 6 T5H tube fixtures on one side. They are end-to-end, and thus gives me 8' of light. I hang those fixtures about 18" above my top shelf of orchids (no closer than 8" from the leaves though). They get hot and I think the total lumens for each fixture is rated around 25,000 lumens. They are really, really bright.

On the other side I have four, 4' x 2 T8 fixtures, placed side-by-side and end-to-end. Again, I have 8' of light but two deep. Each of those fixtures is rated around 5,000 lumens. Compared to the T5H fixtures, though both the T8 and T5H are 6500K tubes, these T8 lights are "dull"! They are also cool and I can place plants within 3" of those with no problem. I am leaving these T8 fixtures as-is for now, but will replace them next fall with the same T5H fixtures I use on the other side.

I have a light-meter ordered and when I get it in I will know how much light there (really) is under the various light arrangements I have in my two greenhouses. I will post that info then.

The T5 arrived and it was so small - just two feet long - it seemed silly when I looked at putting it over my 3' plant shelves. So I returned it and a 4' (4 bulb) T-5 has arrived instead. I'll just let it hang over the edges a bit and provide some light for the potted plants on the floor.

OK, Carol, now you are in my ball-park. All I use are the 4' fixtures. How many tubes per fixture? What is the K? Are they H or HO tubes/bulbs?

@drdawg there are 4 tubes, 30,000 lumens, 6400 K, 54 watt not HO. Milliard brand (fulfilled by Amazon) -- pure Chinese.

Wondering for future in my 12 x 8 (two 6 x 8 joined) whether I should get a four tube - or six tube to hang from ceiling? And, since they really need to be within 2 feet of the plant (?) whether that makes any sense at all. Maybe I just need to hang them all along the sides like you have. We get a lot of sun here during the winter in Texas (just brief periods of overcast, and occasionally a few days at a time) - so our needs perhaps are a little different.

Do you think I need to change the bulbs to more red to encourage the tomatoes to produce?

Carol, I can't answer your question since I am growing tropical plants, mostly orchids, under those lights. My lights are timed to come on at 3:00 PM and go off at 9:00 PM. I am simply supplying more light because the sun is so low in the sky during the late fall and winter months. All my tubes are 5000-6500K, and the new T5H tubes are all 6500K.

Do put your hand close to the tubes after its been on a couple of minutes and see how much heat there is. That's the key element here. My T5H tubes really get hot, similar to an incandescent bulb, but my T8 tubes stay cool. You want your plants as close to the light source as possible but not so close that the leaves would burn. I can put plants' leaves within 2" of the T8 tubes but no closer than 12" to the T5H tubes. There is that much heat difference.

@drdawg thanks. These are supposed to be very cool to touch. I'll experiment and see what I get.

I am anything but an expert here (sometimes I literally know nothing!), and though different manufacturers produce different 6500K bulbs, I would be surprised if your 4 tube fixture produces anything close to 30,000 Lumens. A typical "Gro-light", 6500 K, 4' T5 tube would produce around 90 lumens per watt. You'll have to check your tube wattage, but again, an average would be something around 54W.

Not that this is terribly important. That's still a great fixture to use. This fixture will certainly produce enough light to aid your plants.

@drdawg - you're right -- it's 16,000 lumens. Not sure where I got the 30,000 from - wishful thinking maybe. Got it installed today and was focusing on getting the plants within a few inches of the bulbs ... then remembered your warning. Even though folks on Amazon said it "didn't put out that much heat" I noticed that within 10-15 minutes the heat was noticeable. I lowered the plants so they are about 12-14 inches away now. It's the Milliard brand- was disappointed to see the one page info that came with it (absolutely no warranty) - quite to the contrary, a complete disclaimer of liability ("buyer assumes all risks and liability from the use of this product"). Made in China. I miss the Made in America days - and I keep looking and hoping for more Made in America, even if the cost is a bit more. However, there are good reviews on the product on Amazon, so I think I'm okay. Just disappointed with this new "Chinese tactic".

It sure puts out a lot of light. Looking forward to some improvement in what I'm growing in there.

Still plenty of light, Carol.