Bigtops is right. The more light the better so 24 hrs is best but if you cant do that you have to cut the time down.

You will lose yield by lowering the light time...no way around that. 12/12 though might not be worth the time... ive seen this before, someone using 12/12 on an auto in a different forum. The end result was 3g of bud dried.

Like bigtops said... dial them in and let the go. Thats all you can really do and learn.

400w can be used on seedlings, it just needs to be raised up higher. When they get used to it and get a little bigger you can start to lower the light as needed.

A 400w on 24hrs can add up on the power bill... especially when you factor in the fans and ventilation and what not.


I just finished some automatics like yours... the link is in my signiture down below if you want to check em out and see how I did it. I also used a 400w sodium but I used 20/4 light schedule.