Pygmy cory with damage to face

[Lauralana9]

Pygmy cory. Not sure if there is something growing off his face or that is his face shredded.

Ammonia/nitrite/nitrates :0/0/20

Temp: 77.6 PH: 7.5

10gallon lightly planted sand substrate up since February can't really vac since it's sand but i do a 10% change weekly and "swish" the bottom

Aquaclear 20

Mates: male Betta, 8 other pygmy corys, 1 mystery snail, a zillion MTS

Nothing new for a while now. Betta was the last thing about a month ago.

Everyone else in the tank looks just fine.

 

[Aiken Drum]

That looks like an infection.

Are you able to quarantine the fish and treat it there?

Is there anything in the tank that might have damaged the fish? Is the substrate a nice smooth sand or is it a gravel with sharp edges that could have caused the damage?

 

[Lauralana9]

He is currently in a 5 gal tote with a heater and airstone. No extra filter ready. Had a sponge for this reason but it went into new shrimp tank and I never replaced it. I did add 1 tbs kosher salt to the water.

Sand is smooth there are two dragonstones that I was planning to pull because of the betta but I haven't decided on a replacement so I left them because the corys do like to hide in the "cave not cave".