It looks like the corner with the pool is a bit higher than the surrounding ground. You could use an extra bit of hose to siphon the dirty water out & away. Just stick one end of a hose into the pool and run the other end somewhere lower, preferably where you want the water to benefit some...
The coop & pen look great, and so do your birds! I couldn't see or hear enough details from your ducks to help you determine their genders. I go by their quack/rasp and the little curled feather on the drake's tail.
Now how do you plan to drain & clean that pool?