, Moon lights / Lunar light systems don't hurt the inhabitants of aquariums. It doesn't necessarily help them either. I have lunars on three tanks. I don't use the moon settings every night, sometimes it's all lights out.
Lunar lighting is just a nice optional addition. The good ones cast shimmering light, gradual light intensity fluctuations or even thunderstorm w/lightning simulation.
Some fish and inverts are nocturnal. The Lunar systems allow more frequent and brighter viewings.