Help! My Gourami has a problem.

[Diana]

One possible bacteria that can make ulcers like this is Aeremonas. A nasty infection. Quarantine tank for sure.

You can treat it externally with either of these methods, but ONLY ONCE.
Catch the fish, and hold him so the wound is exposed to the air and put on a single drop of hydrogen peroxide OR one of the vaseline based antibiotics like Neosporin. Use a cloth soaked in stress coat to hold him.

More treatment:
If he is still eating then use antibiotic treated food, perhaps an antibiotic like Kanamycin.
If he is not eating then use an antibiotic that will be absorbed from the water.
I would also add a small amount of salt to the water, 1 teaspoon per 10 gallons to help with stress.

Care notes:
Keep the Q-tank bare bottom and vacuum daily to remove fish waste and uneaten food. Bacteria can live in debris.
Keep the tank warm, and the air above it warm. Gouramis are labyrinth fish, and need warm air above the tank.
Fish are in less stress in darker surroundings, and if they have a place to hide. I would trim the plants in the main tanks and let the trimmings drift in the Q-tank. They will make some shade and hiding places near the surface.

[mistergreen]

Hey, that neosporin idea is a good one. It'll protect the wound too. Use gloves. You don't want to infect him or you catching it too.

[Wannaberooted]

Unfortunately, before I could try anything else, he died. Poor guy, he was a good fish. He also had long stringy poop, which I also saw is a symptom for DGD. My water conditions are good, I'm hoping it was that and I don't have any more problems with the other fish.

Thank you everyone for your advice, but if it was DGD, there was nothing that could be done. I won't get another Dwarf Gourami, though I really like them.