He would not go in a 20 gal. Sorry if I confused you there. He would go in my 55gal. tank. 14" is over the size. Below is a description from a website I copied from the Internet. It states they are mature at about 4.5". I have had Chinese algae eaters before and they never exceed 5". They do not outgrow their environment.
Thanks for reading!
Description:
Not the most beautiful of fishes, the body of the Chinese Algae Eater is plain with a notable black stripe from the tip of its "nose" to its tail. Though their color is quite variable, they are often yellowish on the sides, more brown along their back, and have a yellow eye. The stripe is often broken, and there can be black spotting along the back and at the base of the dorsal and caudal fin. They have an under slung mouth which forms a sucking disk, perfect for anchoring to a surface especially in fast moving water.
Size - Weight:
They grow up to 11 inches (27 cm). They are mature at 4.5 inches (12 cm). Personally we have seen them at 5 inches which is a surprisingly large fish, but we have never seen one approach 11 inches.