Seedling help

I have about 15 seedlings that just popped between yesterday and today. I first had them outside in the natural sunlight, but tonight I want to move them indoors. I have a 400w Metal Halide in a small room about 7x7ft. On what kind of light schedule should I put them on? I was thinking a 16hr light schedule would be good, but what do you all think?

Most people say 18-24 hours. I did 19 hrs and it works great

The more light the better...make sure it stays cool around the seeds...too hot, and they will burn up...try a CFL for seedlings, this way you can get the light closer without burning them, cause the CFL will emit less heat then the MH.