What the mess is this?

[Modest_Man]

I agree. ^^ It looks like an ulcer.

Melafix is like snake oil. A salt dip might work as well, if you don't want to treat a whole tank with salt. Or you could also swab some medication like Neosporin onto the affected area.

 

[Taz2478]

Robitussin cures all

 

[Nic]

Q tank with some salt and maybe a dash or 2 of mela or pima