What BB was in that tank was probably long gone. A QT tank isn't goin to have a well established biofilter anyhow, considering what a QT tank is used for. daily WC's will eliminate the need for tank cycling in that hospital tank...focus on the fish's getting better.
I don't understand; wouldn't tending to the hospital's water quality be part of focusing on the fish's getting better? Didn't we just say that there's not much else that I can do?