Thank you He went to a photoshoot that a friend arranged. I'll post the full one
I took better pictures tonight. It wasn't as bad in that photo but now it looks bigger. My tank is very clean, the water is exchanged 50 % every two days, I'm not concerned about any rot or fungus. I have zebra snails, their shells are very hard. Only snails he can't eat in my tank. I'm wondering if he cracked or chipped it that way? He has a rock but he doesn't go near it.