is it ok to stop flooding when its dark time?

[dunno]

When flooding your system is it ok to stop flooding when its dark time?

I dunno how this flooding works in the 2 liter bottle setup. When you say flood every 20 min, do you mean like if your lights go on at 5:00 am and off at 11:00 pm, and your pump goes on at 5:20 am then 5:40 then 6:10 then 6:30 and so on till the lights go off???

What kind of timer would you need?