i would agree with Natty, 14 hours is to much
But i also think 6 - 8 is way to little
Most run in the range of 10 - 12 hours
I run 12 hours total of lighting , 07:00a - 12:00, then off from 12:00 - 16:00, then back on from 16:00 - 23:00.
@ 1.3 WPG and dose with Excel daily
Algae growth is minimal and the plants do not seem to even notice.
always keep in mind YMMV