I am somewhat cross posting this question from Tropical Fish Diseases, but wanted Anabantid specific advice as well.
Until a few days ago, I had no QT tank at home.
I have an established 55 gallon tank to which I added 2 Dwarf Gouramis back in Jan or Feb 2014 (aquired from Petsmart or similiar). One seemed terribly stressed from day 1 and died within a couple days. The other was hardy and has done quite well.
After a couple weeks, some of the established fish started looking stressed. I treated the whole tank with Quick Cure and everyone soon returned to normal.
I decided I wanted a 2nd dwarf gourami, so acquired one about 2 weeks ago from a LFS with a good reputation. In recollection, the dwarf gourami had just come out of QT in the LFS that same day and looked stressed (rapid respiration) in the store tank. They assured me all was well, so I took him home. Immediately the resident gourami started hanging around him and chasing him. The new gourami remained stressed looking. After a few days, I found the new gourami on his side at the bottom of the tank, apparently dying (barely breathing etc). I removed him from the tank and euthanized him.
The next day, the resident gourami started looking stressed/hiding/fast respirations/looking abdominally bloated. And within 2 days, some of the other fish in the tank started looking stressed, too. And swimming kind of weird. Moreover, the gourami started drifting in the tank, hanging out in the tank at an odd angle (45 degree) and occ curving into a c shape. Seems he started having trouble moving about in the tank.
The LFS tested my water and found high nitrates, so I did a 50 percent water change with gravel vacuum, added aquarium salt and I treated the whole tank with Quick Cure x 5 days. Everyone looks normal now. Except the gourami. He still looks bloated. Normal waste that I have observed. Still hanging low in the tank, but not at a 45 degree angle. He is eating, but slowly. He is swimming to the top, but slowly. I don't see him curving into a c shape. Overall,he's better, but not well.
My QT tank was just set up a few days ago and cycling encouraged by adding water and material from the 55 gallon tank. Ammonia and Nitrites at 0.25 this morning. Nitrate at 5.
Do I move the gourami over and try to treat with Erythromycin? Or something else?
Thanks in advance.