The CB butterfly is not my favorite fish either. I kept a big specimen in a 30gal hex for years until I sold the tank, and haven't been able to keep them since. Then again, I typically hate butterflys with the exception of the longnose which seems the hardiest of the lot.
The CB butterfly needs to be treated like an angel fish. Only use established tanks 50gal or larger, your PH
must be stable, very low nitrates, and the specimens you buy must be eating and active. I woulnd't touch a butterfly unless it's been sitting at th LFS
for a coupe of weeks and eating like a pig.