I notice it looks like he's in the tank by himself. Goldfish are very social animals and are constantly swimming together and rubbing against each other. He is just very lonely and following his instincts. I can reach into my tank and pet all of my goldfish easily. This is the main reason why I don't even own a net for them. They see my hands constantly with the food and when I'm cleaning the tank. All of them (even my babies I've only had for a month) will let me catch them and pet them.