, looks like a clam shell or something I guess
If it bothers you, you can scrub it off.
Tank: 55 Gallon
The equipment: Coralife 4x65w (2x10k; 2xActinic), Emperor 400, 2 PH
The Fish: black maroon clown, neon goby, yellow watchman goby, 3 blue-green chromis, royal gramma, and a yellow clown goby.
The Coral: zoos, kenya trees, shrooms
, leathers, hammer, and star polyps
The Inverts: LT anemone, pistol shrimp, urchins, etc.
The Janitors: nassarius snails, turbos, hermits, several brittle and serpent stars
The Rock: 68# of Keys-12# Base Rock; from LR