Buenos Aires Tetra with hole in its side.

One morning i woke up and couldn't find my very active Buenos Aires tetra. So i started looking around for it. When I found it, it was in the corner of my tank and had a good size hole in tits side. I immediately separated it from the rest of the tank and put in a separate tank. I am wondering what could have caused such a deep hole to the point where you can see its ribs? After a few days I went to my local fish store and purchased a bottle of API MELAFIX which is supposed to help repair open wounds. This is the first time this has ever happened in my tank. Did I do the right thing and is there anything else I could do to help it recover?

Melafix and aquarium salt is what I would use to treat him/her. What other fish are in the tank? I doubt your tetra managed to bump into something hard enough to tear it open. Also, can we have a pic to see how bad it is?

A turquoise rainbow fish, a normal rainbow fish , two black neon tetras, two clear catfish, two abino bristlenose plecostomus, a stripes raphael, and a congo tetra. Demeter32 i uploaded an image of the wound

Here is another image

Ouch, poor little guy. Is his little arm fin still there? It's hard to tell in the pics. I've had a trio of turquoise rainbows before, and they often fought with each other and a few of the other inhabitants. I don't think the rainbows are the cause though. It might of been one of the catfish, but I still doubt that as well. Hmm...Well, keep treating him with the Melafix and hopefully things will heal up.

Just letting you know, the tetras, rainbows and glass catfish prefer to be in school, so 2 might make them a little skittish and fin nippy.