I put him/her (couldn't sex him/her as moult was distroyed grrrr) in a new tank earlier. A bit of a hair flicker, but calms down pretty well.
Majority only grow to approx 9inch, its down to diet and other factors, its only the extremeties that grow that large... I hope yours turns out huge too tho!!Will be once s/he is 10 - 12", lol