Yeah, I remember those RTCs. Is the Oxydoras niger, TSN, and the two big silver aros still there with them? I thought there were two though, not three.
All animals exhibit variation in the final sizes. RTCs are no exception. The biggest ones I've heard of in captivity were 4' TL. The biggest ones reported in the wild reach 5'-6'. Those RTCs at "The Fish Place" reached ~3' in only 2 years time. RTC's live for up to 50 years or so. They will keep growing. My acquaintance Taksan has had a pair of RTC's in a 15,000 gal pond for 27 years. They reached 3.5'-4'.