It is also best to have this period kept regular, and some plants like crypts will melt with large rapid variations in photoperiod, so a timer is strongly advised to keep things constant.
Photoperiod: The final all-important factor in lighting is the photoperiod, or the length of time per day the lights are left on. To encourage healthy plants and prevent algae growth, a total period of eight to ten hours with an uninterrupted dark period of 12 hours is recommended. It is also best to have this period kept regular, and some plants like crypts will melt with large rapid variations in photoperiod, so a timer is strongly advised to keep things constant. For those of us working during the day, it is certainly also an option to split the photoperiod into two lighting blocks (even or uneven) so you can enjoy your tanks in the morning and at night when you are home. A block should be at least three to four hours in length to allow plants to gear up for photosynthesis and have some time going flat out.