Its 18/6, not 16/8.
Cuttings are known to like 24/0. Thats fact. Its for rooting. Whether plants do is debatable.
Personally, I don't use the 18/6 schedule until a few days before flowering. I keep my seedlings under 24/0 fluros until they are ready for the Metal Halide, then they go under there 24/0 for about 3 weeks. Then, if I didn't top the plants, I switch it to 18/6 for a week before flowering. But its not necessary.
If I topped the plants, which I always do now that I'm growing hydro, I leave it 24/0. I do this because when I topped the plants I put them under a lot of stress. And when you change the light schedule, you also stress them. I don't want to stress them more then I have to, so I just leave them be if they're topped.
Really, it doesn't matter too much. Some will say the plants
need the dark period. But thats just BS because my plants turn out awesome without a dark period in veg.
