Great looking fish. I would feed massivores. What has worked for me in the past is to get a hardy "tough" fish like a Red Devil that is about 3/4 the size for him to chase around. I had a Blue Dragon with waterkok and had a RD abotu 3/4 his size. He would chase him around all day but he was big enough that he didn't get killed. My BD's kok just kept getting bigger and bigger.