Interactive aquarium screen savers?

Hey, does anyone know where I can get a really awesome aquarium screen saver? I'd also like it to be interactive (so I can choose, feed, etc. the fish) I'm not even sure you can get them, since a screen saver goes off when you move the mouse, right? My laptop is Microsoft Windows, Dell, not sure if that's got anything to do with screen savers but yeah... sooo thanks in advance.