It's been tested more than once, and with the 6 hour dark period it does grow faster. The only time you should have it on 24/7 is the first 1 or 2 weeks.

Then the plant's cells react better to having a dark cycle and it makes more energy and puts it all in to the plant during the light cycle.

It's like charging the plant up ready to make new growth.
LIP Reviewed by LIP on . 18 or 28 hour day ??? what about it folks... any input??... what about growing plants under an 18 or 20 hour day.... instead of 24.. Rating: 5