Fish without balance - what to do?

[Saxman]

I recently combined my 29g and my 20g into a 75g. This was done about 10 days ago. It is a planted community tank and everyone has done fine except my Cuckatoos (Apistrogamma Cacatuoides). 2 days ago, the female became listless and the male was not showing his fins - keeping them closed most of the time. Yesterday morning, they both spent the day mostly in hiding. By last night, she was laying on the bottom of the tank. I panicked and quickly set-up the 20g as a hospital tank (the 29g has some new fish quarantined before entry into the 75). I took the water from the 29 and some new water. It just looked like they were not going to make it in the 75, so I felt anything was better. I put in a 1/2 dose of Wide Spectrum medicine. Well, today the female is still alive but cannot keep her balance. The male is still listless although he still eats when I put in food. There are no outward signs of illness. It seems probable that somewhere in the move, I didn't handle things right although all other fish (about 25) are all doing OK.

Should I try to treat them further? Should I just wait? Should I kill the female in some humane way?

Any help is appreciated. In the past, most illnesses I have dealt with were either Ick or just old age/dying type thing.

[Wasserpest]

Was the 75 gal cycled when you moved the fish in? Did you test for Ammonium and Nitrate?

[Saxman]

I used the old gravel from the other 2 tanks - although I did clean it - and used the ECCO filter from the 29 with the same filter material, except I cleaned the pads. The biological filtration should have been good. A few days later, I mixed in some of the old Ehfisubtrat with the second ECCO that I added for filtration.

I do have DIY CO2 so I tested the PH. It is a little high, but my water always has been - 7.5, so there doesn't seem to be too much CO2 which was my first thought.

Nitrate is between 0 and 5 ppm. Don't have an Ammonium test kit.

[Wasserpest]

Actually I meant Nitrite, not Nitrate, sorry. There is always the danger of an Ammonium/Nitrite spike in a new tank, although by using the established filter, it should have been small... But it sure sounds like it, and the A. cacatuoides could be the most sensitive fishies you have.

[Saxman]

Nitrite is 0

[Saxman]

Well the Female died, but the male seems to be doing much better. Since he is now in a tank with medicine, I am thinking it must have been some kind of disease.