Clamped fins are almost definitely a sign of a problem. I'm not really an expert in fish medication myself as I have more of a tendency to let nature run its course (I have a lot of fish o.o), but ask in your local pet store and mention the clamped fins particularly.
I'd move him into a jar for daily treatment instead of his larger aquarium, and drop the water level down so that all he has to do is raise his head to breathe and not struggle towards the surface.
When changing the water, always use a water conditioner - leaving it out for 24 hours used to be okay, but some years ago the water treatment plants changed their standards and they now treat the water with chloramine as well as chlorine. The only thing that will get rid of the chloramine is conditioner. Prime or Amquel will do it.
Aquarium salt is good - it's a very nice all around treatment. Bettas can take it in pretty high doses too. You can also use Plain (non-iodized) table salt (it's pretty much the same thing as aquarium salt) (just don't use iodized salt!).
Keep the other fellow away from the sick guy in case it's a disease that can travel. Don't use the same netting on them and don't put your hands in the healthy guy's water after working with the sick fellow.
(sorry for the delayed answer)
--- In CaliforniaBettas@yahoogroups.com, kiwiya <no_reply@...> wrote:
> I ended up getting two betta fish, one rather unexpectedly. The one that's sick is a black orchid crowntail. He's pretty listless and lately has taken to lying on the bottom of the tank sometimes, or on top of the filter. The fins are clamped and he seems to be breathing rapidly (that's what it means when the gills are constantly moving, right?) I don't see any signs of parasites, his eyes are normal, and there might be a slight problem with the swim bladder but I've fasted him without any results. His rear end hangs down so he's at a diagonal when he's not moving, generally. There's no bloating, though, and he was like that when I got him, so I'm not sure if that's normal for him.
> I'm not sure if it's the water quality he has a problem with. My other betta uses the same water, and seems to be fine. I just leave the water out for 24+ hrs before changing, and I do a little acclimation when putting the fish in the clean water. Both have filters and a heater. The sick one is kept in a tank around 2.3 gallons or so.
> Does anybody have any advice? I've put in a little aquarium salt in his water, but he doesn't seem to be doing any better. I'm really not sure what to do since I can't figure out what's wrong. Should I try a general anti-bacterial medication?