400w fast and vast auto

Day one of my feminized auto flowering fast and vast seedlings by heavy weight seeds from herbies.. there under a 200w 6400k bulb for about 2 week 18/6 until a bit bigger for the 400w hps was going to use a 600w but am using a 80x80x160 grow tent with cool tube and carbon filter and fan all 5" think thing's could get hot..question is once it starts flowering could I put into a 12/12 cycle?

I know they can go 24/0 flowering but would 12/12 do the job and have a good yeild?

Autos will finish under any light cycle you give them. I've never tried it myself but I've heard that 12/12 will reduce yields. I always use 20/4 to give a little dark time

Yo do either 20/4 18/6 or 24/0

I personally like 24/0 and I randomly give them 4-6 hour nightime once or twice per week. With 12/12 you will lose yield!
I also give them 24 hour darkness before harvest.

I might go with 18/6 then..take 8week from germination to bud... day 2 of seedling and they have shot up to about a inch and half showing there second set of leaves... there under a 200w 6400k cfl till there a decent size for the hps...