I had a Common Pleco when I first set up my 29g years ago, I had him since he was about 1.5" long, he grew to be 12" in the 29g, after 4 years moved him to the 37g I currently have, he was in there for a yr or so. I had to rehome him cause he got to be about 16-17" and he was about 6-7yr old, that was 3 years ago, he should be about 9-10 now and I guess maxed out at 19-24" now, if the person who bought him still has him.