Pale and skinny Swordtail

[GumboJones]

My male swordtail seems to be getting sick. He is starting to get pail, sort of skinny, and almost seems like his body is bent a slight amount. I'll try and get a picture on here, but has anyone a swordtail do this? I've had him for a year and a half, and he was fairly large when I got him. Is it possible that he's just getting old? I've been increasing water changes just in case.

[Cichlidsrule]

When your fish is sick, the first thing you always want to do is check the water's pH, the ammonia levels, and the nitrate/nitrite levels. Your LFS should do that for free.
If everything's normal, then the most likely case is fish tuberculosis (or TB). The first thing you want to do is [u]immediately[u] quarantine the fish, as fish TB is extremely contagious. Take extreme care while transferring the fish, as fish TB can be transmitted to humans through open cuts. There isn't anything you can do for fish TB unfortunately, so to avoid causing the fish more pain, I would advise euthanizing the fish. You can do this by buying pure clove oil, pouring it in a plastic jar, and mixing it with some water from your fishes' tank. Shake it hard until it turns white, and place your fish in it. The fish should quickly and peacefully go to sleep. The clove oil acts as an anesthetic called Eugenol, so you're basically overdosing him with eugenol.

EDIT: Here's a picture of fish with extremely progressed stages of fish TB.