Yeah I had one before I gave a friend him and the tank, and it was only a 55 gal and I think he moved it to a 125 not sure though, but I was told he would be up to 18 inches at the least, so that seems as if he should be in a tank larger than 55 gallon when he's full sized. And Dan mine was very friendly, I was lucky! But I did make the mistake of feeding him brine and bloodworms when he was small, and now he almost refuses flake or pellets so its good that you have him eating that as well, because mine did hold out like someone else said, he only wanted frozen or live foods. And he did eat guppies quite easily and VERY fast! so beware he will eat those neons. But it is one of the coolest fish I ever had, he did remind me of a dog
They are really neat they way they swim though. If you work with him, he should begin to handfeed, and hopefully won't hide all the time. Good luck with him!