I think it's nice to have but not neccessary. Like Rockdog stated, it's believe the emulating moonlight will encourage fishes to spawn since some will on spawn under time of teh month according to the moon.
I like yhe looks of moonlights. I also like to slowly turn off and on lights in my tanks. I know I do not appreciate a bright light immediately in the morning to wake up or complete darkness all at once at night. I think all the tank occupants appreciate a gradual change from light to dark and dark to light. Just my personnal opinion. (less stress on critters)
I know when I run my moonlights I get hundreds of baby snails. When they are not running after a while no baby snails. Turn them back on and I get baby snails again. Since I love the looks of the moonlights and the baby snails are neat I now have my moonlights on a controller to match the moon phases.
