They get between 3-4.5 feet. Look up videos on YouTube, they're a very long and slender catfish, they require a lot of space just like a retail cat, I've heard storeis of their very stong boney skulls and "beaks" breaking a 125 gallon tank when theyve smashed into it while chasing food. It would be able to live in it a long time but I don't think for life, just google as many care sheets as possible and they should give you a ballpark of minimum gallons, also size. Many care sheets for rtcs say 4+ feet, but that's in the wild when they can eat in controllably and anything possible, I believe the biggest one in an aquarium was jJUST at 4 feet. But was in a 10,000 gallon pond.