THE FOLLOWING TEXT MAY BE AN INCITEMENT FOR FLAMING. PLEASE DON'T FLAME ME.
Well, I've had 2 ID sharks in a 60 gallon tank for about 7-8 years (estimate). The bigger one has reached a size of about 18 inches (stunted, I know) whilst the smaller one may be less than a foot (HORRIBLY STUNTED, I know). When I got them, I was young. I didn't know any better.
Now, seeing that I'll be moving to a new house soon and my dad has a good amount of space in the back of his office, I'll probably negotiate having a pond made for them.
Just wanted to share a bit of info. Of all the fish I've seen, I honestly feel that Pangasius are the ones that end up stunted the most.