DISCUS: Heavy Gill Movement

I have a 4feet tank cycled for 3 weeks. And during those 3 weeks I added
a Congo tetra and a Rainbowfish to speed up the cycle. Nitrite is 0 and
Nitrate is tested low. I added plants in the background for the full length
of the tank. Mostly Hygros, Anubias and Ludwigias. I have added a Leopard
Snakeskin Discus yesterday after 30-minute acclimitization (sp?).

The Discus does the expected dashing around when I approached the glass but
for
the most part he looks OK hanging very still at 1 side of the tank and
occasionally
venture to the other side when light is off. The thing is I notice his gill
cover
opens real wide as if he is breathing heavily. I initially thought of it as
gill fluke
infection but I didn't notice any scratching on tank objects. In fact, when
I introduce
a juvenile Leopard (which I had for 6 months), they seem to get along OK. No
darkening,
no other anomalies on the skin, no white feces etc. The tank now also houses
4 active
Ottos, a foraging Ram and a shy Dwarf Gourami.