discus gills

[Marie Weiler <MarieW@marquand.com>]

Dare I venture an elementary question regarding discus. I have two
wild-caught green discus, which I've had for a month in a 100-gal
semi-community planted tank. We've recently noticed that the smaller one
(about 3" diam) is breathing very hard, i.e., gills expanding and pink
insides visible. The larger one (about 4" diam) seems to expand almost as
much but on just one side - the other side seems normal (tho we don't really
know what normal is). Also, we've been unable to see the smaller one eat for
the last week or so (originally the larger one would butt it away from food
and now it seems to have quit trying to eat). I've also been fighting
blue-green algae and just last night discovered I had zero iron in my tank
(we are now treating all of this), but ph has been constant at about 6.2-4
and nitrates at about 10.  Does it seem likely that the fish have just been
stressed by the algae or lack of iron or some other element? (all the other
fish in the tank seem hunky dory) or is this a disease symptom? (gill
flukes?)

Thanks for any help and advice,
Marie Weiler