My ducklings live at my mom's so she's learning a lot, falling in love, and asking more questions.
She uses a large plastic kiddie pool, changing it every night but, she was talking to a friend who raises ducks and they told her ducks liked dirty water because they eat the bugs that accumulate in standing water, etc. My mom says the girls do not seem to like dirty water, maybe because I had changed their water so much because... well, y'know they're messy

How often should you change their water?