Loaches Online Forum

I have a 125 gal river tank with 6 large clowns. They fight mouth to mouth frequently. Just noticed one of them has a very swollen, white mouth. Is this from fighting or something worse!

An irritation, such as from fighting, can get infected. White is more often fungus, red tissues more often suggest bacteria, but this is by no means always true. I would do a few extra water changes, concentrating on vacuuming the caves and corners and any other areas with less water flow, especially if this is an area the Loaches hang out.
Keep the NO3 level as low as possible. Certainly under 10ppm, lower if possible.

Monitor the Loach with the sore mouth. Is he eating? Is the swelling going down? Is the white getting larger, or growing fluffy? Is there other signs of infection, such as red streaks radiating away from the mouth?

Look up pictures of fish diseases and see if you can match what is going on with your Loach.