I've seen some around 15-17 inches and the Frankfurt zoo. I would not buy one if you are unable to feed it frozen or live food it's entire life. Very rarely will any individuals convert to pellets. Most starve first.
i had 3. tried it for ages but the best I got was to get them on freezed dried blackworms.
they did try colour/tetrabits, they split it out straight away (thought from reports this is one of the food others have accepted).