MH Lighting for seedlings

I have not used MH light before but got one, a 250w. I was afraid it might be too intense for new sprouts so put them under a 90w led ufo. That was a mistake, they stretch a good bit. So now they are under the MH at about 3 ft. I'm thinking of gradually lowering it now. Is there some kind of rule of thumb for how far above the green a light like this should be at what age?

Thanks!

the only rule of the thumb is actually the rule of 'back of your hand'. put ur hand at the top of the plant and lower the light until it feels like a nice summers day, if its burning your hand then ur too close, if you can barely feel it then its too far away, this is usually between 12" and 18" but theres no exact science to this. having a fan blowing between the canopy and the light is also helpful.

In my experience, the plants can take more heat than you think they can. I usually kept the 400w lights at 12" or less, but I had really good air flow across the tops. I had one girl actually growing the main INTO my hood, and every time I moved her, she moved back!!! I finally super-cropped her to stop it. You'd THINK that if there was too much heat, they'd avoid it.

To control seedling stretch, I've had very good success using a 13W cool white (6500K) cfl bulb less than 2" above the seedling. It's a very cheap and very easy solution.

Hello this is my first post...

I am into my 5th grow indoors....and I use a 90w UFO led for my clones....and what I like about it is...I take clones right before I go to 12/12..so I have 8 weeks to get them ready for the grow room....The rate of growth under the LED is just right, so they don't out grow my clone buckets....

I leave the light on 24hrs about 10-12" from plants...I think leaving the light on 24hrs helps them get bushy,and don't strech to bad....

anyway I like my LED for what I use it for....then I put them in my 10 by 10 secret jardin with 4 1000w HPS....I have to have my son come by and show me how to put PICs on here....

Dura72 has the right info.^^^^^^