Moonlight

I have noticed that every night all of my soft corals close up within 10 minutes of the moonlight turning on, and sometimes my hammer coral will close a little too? All of the corals are healthy and growing. Does anyone have any Ideas why this might be occurring?

Tank specs:
75g tank
20" sump
coral life 80g protein skimmer
Filter socks (changed daily)
Weekly 5g water changes
Salinity 1.0245