we had one at a store I used to work at. when we got it, he was around 12-14" long. about a year later I went back to visit and he was about 2' long. It was in a ~800-1000 gal pond (indoor) with some sharks and large morays. they got rid of him because stupid people putting their fingers in the tank and getting bit.
Even though there was signs all over the place "do not stick hands in pond" people dont understand that these animals bite.
one guy had to go to the hospital for 7 stitches....idiot.
so anyway, yes they are doable, but I dont recommend it.