Goldfish mouth tearing apart

[Jbreezy]

Hi - I'm not sure what's going on with my goldfish's mouth, but it's stretching and tearing apart.this has been going on for a couple of months. He otherwise seems healthy. I removed all of the small rocks from the tank, but he still has this problem. It seems worse some days than others. It doesn't look like the mouth rot pictures I've seen online...it's more of a transparent tearing

 

[Delapool]

Hi, welcome to AA. I can't think of anything off the top of my head.

Anymore details - tearing in same spot?

Also have you checked water chemistry eg ph, ammonia, nitrates.

Are you feeding a good quality food?