CFL Temperature (K) for seedlings

I have an old aquarium and hood I was going to use to start my seedlings in. What is the correct K value for the bulbs I should use? How many hours a day should I run the light, and If the light sits about 1 Ft. above the seedlings, will 2 bulbs be sufficient or too much? Thanks.

I’d drop down to about 6-8 inches and run 24 hours on first 2 weeks. I use a 55w 5600k for my starters


Is that 55 watt actual draw or 55 watt equivalent, or does it matter? Thanks.

True. It’s a big bastard. About the size of a 24oz can
Got it from Batteries and bulbs

Seedlings don’t need a tremendous amount of light.
Anything 3500-5500k should work. 24/7.
I hang a 60 watt equivalent cfl over my seedlings. Usually 4”-8”. You don’t want the lights shedding too much heat onto the plants, they’re pretty sensitive.
There’s a sweet spot. Too low and they get burned, too high and they stretch. Best to err on the high side, since you can replant them deeper if they stretch, but you can’t bring them back from scorched.


I have seen some posts and talk on podcasts about 6500k being really really good as well as it has more blue I believe.


As drink said 3500k + will work but as @Dbpooper stated 6400k is ideal.
6inch is really the max height you want, anything after that and CFL’s light concentration drops off significantly.
The most important thing is to watch your plant /node spacing for what you want to achieve.

You didn’t give us alot of info on the size or Wattage of your light/fixture but I’m sure it’s enough for seedlings. The only question would be when to switch it to a bigger light.
I use a 200w 6400k CFL to grow my plants and they can usually stay under it for the first 20-30 days.
As for hours, if they are autos run them 20/4
If they are photos I would just do the 18/6, although I know some do run 24hr for a bit at the start I never have and never seen a reliable source/data to back it up

My idea is to purchase a single or double bulb ceiling fixture that I can attach to the underside of the aquarium top, which will likely be plywood, and pop one or two cfl’s into it. This would make it a bit larger than the plastic seed starter with dome I’m using now. Would actually like to put together a few of these if they work for my smoke crop as well as starting flowers for the wife to use in the yard this spring.

Seems like a cool idea that would work.
I woild stress coating the plywood with flex seal or something because the mosture on the plywood will lead to issues and eventually rotting.
I take it you have some aquariums. Laying around? Because you can get min tents for cloning /seed starting

Thanks @Nicky for the coating hint, I’m still deciding how to handle that. Also wondering if It would be beneficial to paint or otherwise cover at least 3 sides with reflective material. I always see many small tanks on FB, Craiglist, and Goodwill stores (I find all kinds of stuff there to re-purpose for my grow room). Have I seen in the past that you start autoflowers in peat pots? That’s what I’m trying now, and It seems to be the best start I’ve had so far, but I’ve only been at it about a year.

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Yes peat pucks are the best I find, but you need the dome with them to really make sure they stay humid.

If you don’t have the aquariums laying around then I would suggest instead using totes/bins lined with mylar, they seal, they don’t rot, you can easily modify it.
You could do a clear one or not.
Or buy a clone tent

Make one of these…
Works like a charm…

12 cfls at 6500 Kelvin at 23 watts …


Heres what they can produce…

In a 2x4 space … no tent…lol


@Nicky: To pick your brain a bit more, do you: 1-soak seed in a cup first? 2-paper towel? My pellet success, using both small and large pellets has been 50-75%. This is my first time with peat pots. I used pre-moistened, off the shelf, seed starting medium. 3 for 3 using this method.

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Wow, great use of space!

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I soak my seeds for 24hr
Boil water, pour it into the jiffy starter (this warmth helps but also kills any bugs in the pest Puck)
Let it cool a bit to warm, loosen the top little layer with a knife and just barely burry the seeds with loose material so light doesn’t penitrate.
Close the jiffy dome and place it somewhere (I usually put it in my pantry because it’s a nice solid stable warm temp there).
Keep it moist with Ph’d water
When transplanting them just before they hit the roof (so that the roots don’t reach through the mesh) be sure to cut the mesh off and burry them as they will have stretched a fair bit.

Thanks for the tips

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@Nicky, I should have asked earlier. I have 2 sizes of pucks on hand. One, when expanded, is about 1.5" that come with a domed tray about 4" high. The other pucks are at least twice the size, and a domed tray about 10 inches high. Which configuration works for you? Also, I have never cut off the mesh, and also had varied results. Do you cut it off carefully with an exacto blade, and is it better to do it while pellet is dry or moist? Thanks again.

I have the smaer ones, never seen the bigger ones.
I cut or just rip the mesh off with my fingers before transplanting.
Some say the mesh doesn’t matter and to leave it alone but idk, I’ve seen roots grow through it and they grow thinner through it so in my opinion that is a bottleneck

So with a small puck/dome, your seedlings don’t have too much in the way of leaf development before transplanting? Roughly, how many days from the day it pops out of the puck until it goes to its forever home?