help with gourami...trouble breathing and swimming

When I turned on my aquarium lights, my opaline gourami went crazy and then just fell to the bottom of the aquarium. It looked like it had a heart attack adn died. A minute or two later, it started moving again, and eventually made its way to the top of the aquarium before falling again. Then it made its way back up and stayed up at the top (i think to use the labyring organ to breathe). But it was slowly pulled toward my penguin 125 power filter and the current (which isn't very strong on my 20g) pushed it down to the bottom of the tank again. Then is slowly swam back out and up to the top of the tank. The gills are still moving very rapidly. Can anyone tell me what happened or what's wrong? I purchased him yesterday with 3 gold skirt tetras and acclimated them very slowly. The other inhabitants are 2 zebra danios.

20g long tank
pH 7.4
ammonia 0
nitrite 0
nitrate 0
20 w full flourescent lights

Edit: The Gourami seems to have lost its color. It's now very pale, and the blue markings are gone, but there are some black markings.

I don't know...if he was sick when I bought him, he definetly didn't show it yesterday or at the store. And I spent about 45 minutes acclimating the fish, so I'm not sure about pH shock. Same thing with the swim bladded idea...he was fine yesterday. But now he's hanging out at the surface, occasionally doing these wierd flips to get back up there, sometimes swimming a little, and occasionally getting pushed down by the return from the filter. He's also staying out in the open, whereas yesterday, he stayed in the area behind some rocks and plants. I keep thinking it has something to do with the lights flickering on, but that doesn't make any sense either. And he won't eat. I turned out the lights for a while, but his color is still way off. The other fish seem normal, although the tetras don't eat much. They don't seem to like coming to the surface to get the flakes. Maybe a sinking pellet food would be better? Are they any foods that sink to about mid-level?