Attached is a photo of a zebra danio with a gaping ulcer/sore. This is my very oldest fish, having come in accidentally with a few feeder guppies when we first started out a few years ago and did a fishy cycle (did not know any better at the time).
He is in a community tank with all peaceful fish, so I am sure that this wound is not due to a bite or other aggressiveness.
I have put him in a breeder box and will move him into a quarrantine tank now.
I don't think there is much I can do for him, but I've never seen this on any of my fish and am concerned that it could possibly be something contagious? Any idea what it could be?
This tank just came out of a 2 week salt/heat treatment for ick with great success.

He is in a community tank with all peaceful fish, so I am sure that this wound is not due to a bite or other aggressiveness.
I have put him in a breeder box and will move him into a quarrantine tank now.
I don't think there is much I can do for him, but I've never seen this on any of my fish and am concerned that it could possibly be something contagious? Any idea what it could be?
This tank just came out of a 2 week salt/heat treatment for ick with great success.
