A good moon is a bright moon. Not just in terms of light, but in mood as well. Like, gee wiz, what a bright, happy moon.
It's so bright that you can see all the roe (ろう) in the sea glowing and reflecting the light like stars. And the tiny baby fishies inside the roe are smiling brightly back up at the moon!
Currently there are no similar looking kanji which exist in the WaniKani learning system