Koi fish being picked on

Clovis CA

Description

We have 5 koi fish in a tank. One has not grown like the rest and is being picked on. They have chewed away most of his fins. Would someone be able to provide a safe environment for him? He stays at the top of the tank all day, every day to avoid them. He is about 3 inches long. All white with a little bit of orange on his head.