when i bought my african knifefish from petsmart, the lady picked that particular one out for me (because i had a big enough tank to keep it in). she said he had been there forever (6 months i think she said). when she caught it, it was 3x the size of the rest of the african knifefish in the tank.
the small lfs has had this clown loach for at least 9 months if not longer. idk why.. its about 6 inches long and looks healthy.
they also have these gobies that have been there for at least 6 months. ugly ass little things no wonder they don't sell lol.
at one point they had a leaf fish of some sort (pretty freaking cool looking actually) for around 3 months the dude told me.