400w high sodium light and seeds

I have my seeds in seed started (riot cubes). Iam going to use the 400w through out the whole growth. (Low on cash) So how far should the light be from the riot cubes ? (Growing in a small grow tent. And any other info i should know pls thanks

U got good vent? Fans? Hps puts out some heat n must be exuasted out. U got pics? N more details

18" - 24" is fine for seedlings.

Done it many times heats your concern until substancial roots developed. If hot keep away and graduate slowly if cold -75 nuke em. Just pay attention to em