Thank you! As long as they don't touch, it sounds like moving the lights closer is a good idea.

My plants frequently touch my T8 fluorescent lights, and there is no problem whatsoever. But once you get a one-inch diameter bulb less than an inch away from the leaves, the amount of illumination they get doesn't really increase that much.

Understand that, at best, the illumination that plants get from such lights is the equivalent of a cloudy day.

Thank you. My lights are definitely more than an inch in diameter, though.

If you have a real concern, as plants can sometimes zip in a day, put a appropriate-sized fan on them. It will disperse the heat, and strengthen the stem in preparation for outdoor conditions.

" My lights are definitely more than an inch in diameter, though."

Then what kind of bulbs are you using?

Dave

i put a PC fan on each side of my fixture, very slight breeze to keep air moving. i'm assuming if yours are an inch in diameter those don't produce a lot of heat because they also don't produce a lot of light.

here is what my fixture looks like with a PC fan on the left. i keep my fixture around 5-6 inches because i use special high output T5 UV bulbs, but it helps give the plants some air and keep the hot air from becoming stagnant.

"Then what kind of bulbs are you using?"

Just measured, and it turns out each light holder is an inch in diameter. However, each actual bulb is 1.25 inches. They're four-foot-long, 40W, cool white bulbs.

EDIT: On second measurement, the bulbs are closer to 1.5 inches than 1.25. Guess they're T12 then?

T12 is an inch in diameter ; T8 is 8/12 of an inch ; T5 is 5/12th of an inch. me thinks.

sey

According to this page, numbers are in eighth-inches. So T8 lights would be 8/8 or 1 inch, T12 would be 12/8 or 1.5 inch, T5 lights would be 5/8 inch.

if they are over 1 inch then they are T12s.. they are very inefficient and don't produce a lot of usable light for plants. you would need around 2-3x T12 tubes to put out as much light as a single T5 HO (high output) tube.

the fixture i have has polished reflectors built in and pushes almost all of the light down where you want it (95% according to the manufacturer). not too pricey either, $90 at homedepot and bulbs are around $10 each. puts out 20,000 lumens using around 200watts. here is the link in case you're interested.

justaGuy17

According to this page, numbers are in eighth-inches. So T8 lights would be 8/8 or 1 inch, T12 would be 12/8 or 1.5 inch, T5 lights would be 5/8 inch

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You are right. I erred.

Sey