Scott Rogahn wrote:

To spare the poor fish from a sudden blast of light in the morning the bulbs
are wired as two pair each with there own timer. One pair will turn on
about 2 hours before the other pair. One pair will also turn off 2 hours
before the other. Sort of a dawn to noon to dusk effect.

This is nice, except 2 hours is not necessary. I've got two timers, each set to
run the lights for 12 hours, circuit A comes on and goes off just 15 minutes
before circuit B.

15 minutes is plenty to avoid shocking the fish, and it makes it much easier to
track bulb life. Remember that flourescent bulb output drops significantly after
6 months! Compare a new and old bulb if you doubt this.