Aquarium adventure one of the LFS's here in Columbus Ohio used to keep and sell Catfish in excess of 24" mostly channels and blues. I haven't been by there for a while so I don't know what they have now. Tiger Shovelnose are listed as growing to 50" I have had a couple but sold them before they passed 12" Somewhere it mentions that the will bust the end out of your tank if they don't have enough swimming space.
