My two runners got on a schedule pretty quickly when we had them still in the sunroom at night. It helped that we already had a bedtime routine for our two dogs. We kennel them at night. If we didn't things we be chewed up or pee'd on. So we had a bedtime @ 9 or 9:30pm and a 6am wake up time for them to go potty. The duck's jumped on that asap. Especially when we started putting them in their pen during the day, that is when they would start making noise and quacking when they would hear the bedroom door open @ 6am.
As soon as I would coral them in their pen in the evening, turn on their light and close the sunroom door, they would preen and bed down for the night. Even though now, they are out in their pen all night, they still want to be let out at 6am, almost on the dot!
They sleep in their pool, but I m not sure they stay there all night? One night I took it out and put them to bed, they seemed completely displaced without it. They just stood at the door and stared at the house. I kept peeking through the window to see if they would bed down and they didn't! They just stood there as in disbelief that I had taken "The Pool".
After feeling guilty, I went out in the dark, put the pool back in their pen and filled it up. They were happy!