I have such bad luck with Bangai's! I think God just doesn't want me to have them... As of now, I am only 3 for 16 with Bengai Cardinal fish. They just do not go through QT very well. I have done 8 pairs of these fish and out of 16, I have only 3 that have made it to my 225G display. I wanted a group of 5 or so originally, but I have given up. Out of the the three in my display, they are doing just fine and been in there 8-10 months. They live with 6 Tangs, 3 clowns, a school of Green Chromi's, six line wrasse, and a few other misc small fish. They hold their own just fine, however, 2 of the cardinals like each other, the third is a total outcast. I have found the outcast living in my overflow many times, as he must be a loner and probably feels like a loser after getting bullied by the other two.
This is my opinion only and not scientific fact by any means: I don't think that these fish do well in copper. The three that I have living in my display, I removed from copper quickly and QT'd them in regular tank water and just observed them. When I felt comfortable, I added them to my display. It is risky doing it this way though. As most LFS run copper in their tanks, I think the damage is already done when you go to buy them. My favorite LFS hates them and says that they rarely eat in the store. This backs up my theory that they don't like copper. I always make sure they eat before I buy them, but even still, they will stop eating at some point during copper power quarantine. I would suggest finding a pair that gets along well in the store, is already eating frozen mysis and brine in-store, and then do an observation quarantine, maybe a "General-Cure" dose at maximum (even that may be risky with these IMO). No Copper...
