Red Minor Long Fin Serpae Tetra sick?
I am new to having fish and have had a tank going for around 3 months with 3 neon tetras, a zebra fish, and a red minor tetra. Over the past few days, my red minor tetra has taken to hiding under the bridge at the bottom of the tank- which is very unusual for him. We were out of town over the weekend, and had the lights off the whole time (but there is daylight in the room), so I suppose that could have thrown him (?). His appetite is good, but he does have significant amount of white under his mouth area, and I'm wondering if someone can look at it and tell me if I should be concerned. It has been there for quite a while now. Oh- the water has been checked and all is well, and the other fish seem fine.
Any advice would be greatly appreciated.