400 watt light question

Quick question;
I have an air cooled 400 watt light (38,000 lumens, MH) that im using for my sprouts. In most marijuana books and web pages, they say that if using an HID light, I have to keep it 18-36 inches away from from my tender babies. The thing is, I think they're talking about a 1000 watt lamp.
My 400 watt is air cooled also, so the light 10 inches from the "canopy" is only 76 degrees.

My question being, is there a rule somewhere that I don't know about that says I shouldn't put my air cooled 400 watt lamp 7-10 inches away from my 2 week old sprouts?

36" works perfect for me with my 400w. Too close and they wont want to grow "up" and they can get bleached by the light.

You can always try and see what you can get away with. There is no set in stone guide, each plant is different and has slightly diff needs. Some thrive close to the light some don't.

Why do you need it closer? Are your sproutings doing bad?

Dirt Bikin Buds said:

36" works perfect for me with my 400w. Too close and they wont want to grow "up" and they can get bleached by the light.

You can always try and see what you can get away with. There is no set in stone guide, each plant is different and has slightly diff needs. Some thrive close to the light some don't.

Why do you need it closer? Are your sproutings doing bad?

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Thanks. Yeah, I guess I don't need it close. I just figured the more light (lumens) the better. Is that not true? Im not being sarcastic, Im seriously asking you. My sprouts aren't doing bad per se, but they are moving pretty slow, but they aren't good genetics either. I got them from a bag of good regs and I'm growing them now to hold me over until I get my seeds from attitude. You think they might be moving slow because I have the light too close? I'd hate to make this mistake with my good seeds...

I have found that by slowly lowering the light to find your sweet spot the plants get use to the HID lights a little at a time until you are there. I use T-5 for the first couple of weeks (after rooting clones) and then go to the MH from a distance a little at a time. Within 2 weeks they are in the sweet spot and had no stress.

Heat is the determining factor. If you can comfortably hold you hand comfortably on the glass for more than 6 seconds, you can put the plants 24 inches with no problem. I like to keep my seedlings under CFL lights 3-4 inches above for first 2 weeks. It saves money on electricity, is cool, and the brightness so close keeps the new seedlings from "stretching and becoming lanky". Good Luck ! thegrowschool.com