I have kept Wallago attu before in the past... very interesting catfish. I raised mine from 2.5" to about 14", they have an extremely fast growth rate. Although it lays still most of the time, it is a v ery strong fish that can attack or move surprisngly fast... w/ bursting speed! I plan on keeping another one sometime in the near future.
Pangasius gigas reaches 10' in length (300cm) while Wallago attu 8' in length (240cm). Not an entirely big difference; especially when you are discussing the attempt at housing one in an aquarium. They are both huge fish that won't last long in your average tank.