Ever recall a time when you were fascinated by fish in a tank, and how they moved? I've always loved watching them as a child, and would marvel over their bright colors and simple objective- Eat food, and observe change. However, they ARE social creatures, despite what many people think. One goldfish on its own, I imagine, would find a lot of interest in its own reflection, even if it would be in something quite small. A lonely goldfish would certainly seek out its reflection now and then, perhaps just to reassure itself that it isn't alone in the pond.