I think my gold fishes are thinking air bubbles as food. They are not always gulping. But occasionally they would go to the surface of water and try to eat small food shaped bubbles. They don't go near big bubbles. My airpump is new and I don't know how to control the flow. I think its making too big bubbles. Anyways, I always turn the air pump off during feeding. I hand feed them so that they get fair shares. But after I'm done they seem more hungry. And then after I turn the pump on they are eating bubbles. They do it for couple of minutes and when they understand that this is not food they will return back to their places. After some minutes or hours they will do the same thing. They imitate the same thing as they do while I'm feeding them. Is it bad for them? Can they have any disease from eating bubbles? If it's bad how can I stop them from doing so?