To treat or not...and how

[flyingdisc]

I've had a group of 5 discus for about a month (from the same person, imported, but grown out in the states, smallest is 4.5in) and there is one I am concerned about. He appears thin (body isn't filled out b/w eye and dorsal fin). He is dark, but he's always been dark, and the tank has a ton of wood + peat so the water and all of the fish are darker. Other then clearly being at the bottom of the pecking order, he acts/looks fine (appetite, swimming, poop etc.). Water parameters are fine as are all of the other fish.

If I have a parasite or other disease in the tank wouldn't I see it elsewhere? I treated w/ paraguard for 5 days because that's what I had around and am debating running a series of Praz and/or Metro (not at the same time). Should I do this? I have some Pima and Melafix around too, but if he's thin my guess was on internal parasites not bacteria. I debated isolating him to treat him, but I am debating the pro and cons of the stress of doing so.

Any suggestions would be great. Thanks in advance

[Eddie]

I probably would have skipped treating with Paragaurd. No use in exposing all the fish to chemicals when you are not sure what the problem is.

From the sounds of it, it may be an internal issue. Possibly nematodes of some sort. Do your fish eat flake food? You could always do a round of deworming, using a deworming flake.

Hows your water parameters? How often do you perform water changes? What size tank?

Eddie