It's not necessary to keep water over the top. That is a personal preference and most of us tend to keep ours on the drier side. I don't want the extra hassle of straining my feed.
@BY Chicken Lady where are you? I am on the Colo. River in AZ.
I am in Central Arizona and SW Colorado.
I had issues with my FF going bad if I didn't keep it wet enough. Its not really a hassle to drain the liquid, I have an easy system that takes me all of about 30 seconds to do, and the reserved liquid is used to jumpstart my new batch daily.