Honestly, I have no clue.
I got one at 2" and 18 months later when I did some major redecorating in the cat tank I found it. It was a fat hog at 6" or so.
I'd thought it had died. Apparently I had such a great hiding place he only left to eat when it was dark. Pretty little catfish that I still have today. He's been with me for a little over 3 years now.