You are going to get alot of exaggerations, 1st off I'll start with a little reality, 20" is the max size in the wild. The common size of these fish, and all fish for that matter, are much smaller than the max size listed. The longest I kept one was 7-8 years and he was less than 7", I got him at about 2", he was in a 180g. I personally introduced one at 5-6" into a 10k gallon aquarium and about 10 years later he was still under 10". I personally have never seen one over 10" in a home aquarium and I have seen many in very large aquariums. They do grow on the slower side, a 2" may reach 5" in a couple years time, then slow a bit, then when reaching around 7" slow more. It is very common to keep these guys going toward 15 years. I've seen a number of them where people had them over 10 years. This is just my take, I am no expert, and others will have varying experiences.
A tip, get a juvi and grow him up, if you get one no bigger than 2", they will grow up much more civilized. Getting them at a larger purchase size usually comes with the super aggressive attitiude many warn you about.
