Hippopotamus Indoor Holding

If the male hippos rotate, then is there always one in this small space for 24 hours per day? How is the pool cleaned? (There is probably an off-show area to place the hippos to allow for keeper access.)

I’m not entirely sure if they rotate every other day, or if they switch sometime in the afternoon, but there was always one hippo in this indoor area throughout the day. Hippos are my favorite so I checked them out a couple of times, especially because the pygmies are right next door. The hippo pools did not look very clean, but the female pool was empty so there’s a possibility they do drain/clean them regularly.