The large pangasiid catfish species are essentially impossible to get to breed under normal aquarium conditions. You need an huge pool (millions of liters) and even then they require injections with hormones to get into the mood. It would be big news if an aquarium ever managed to breed them under "normal" conditions, so gentle lemur is almost certainly right. The good news is that they're quite robust and there's a good chance it managed.
The Mekong tank is impressive. I believe the second largest at River Safari (after the huge Amazon with manatees). Does anyone know the approximate volume and/or measurements of the Mekong tank?