Looks like a scrape to me too. Do you have some rough rock in there?
Looks like it ran into something. My del tries to squeeze into places that are too small sometimes and gets a ding like that. It always clears up in a couple days.
its just from scrapping itself on something,rock,or drift wood filter intakes,or outputs.
Got Pleco in the tank?
Looks like a scrape to me too. Do you have some rough rock in there?
Definitely a scrape from that rock in the tank.