IMO, i think they only host the anemone ONLY when threatened and if there are other fish in the tank as well... like what KEstep said, it gives them a sense of protection, but by day, they don't feel threatened. Daily routines won't scare the clown(s), but i bet if you put a net in the tank, they'll go "running" back to the anemone or lifting the lights away from the tank. If all you have is clown(s) in the tank, chances are they won't need to host it all the time.