fish has developed a black mouth

[jlbacker]

Hello, I'm new to your site. I'm hoping you can help me. I have some black skirted tetras, one has developed a very black mouth. It does not look normal to me. I've tried looking on some other sites for a description of this appearance but have had no luck. Hoping someone here might know what this is.

thanks

 

[Lupin]

to MFK!

Do you have a pic of the mouth? What are your water parameters? There are plenty of questions you need to answer. Check this.
http://www.monsterfishkeepers.com/forums/showthread.php?t=210102