i kept this one in a 55g tank and although it was a little shy at first after a few weeks it spent most of the day out and about. pretty good eater too- meaning it was able to get its share among some other fast swimmers in the tank, and it ate whatever i fed the tank (flake, cubes etc).
i'd be very surprised if there was a problem with it and a firefish, in fact, i'd think they'd make good tankmates.
greg