This may sound a bit childish of me, but I have a fish that I think is dying of loneliness. It is one of three Panda Corys in my tank, and it is smaller that the other two. It has recently started spending its time lying in one spot, not moving, not eating, not joining in the constant digging for food (I should also add that it was never as active as the others ever since I got it a few months ago). It seems that if there was a disease, there would be visible signs by now, and/or the other fish would be affected. Is it possible that the smaller panda is lonely, or am I just applying human feelings to a fish because I can't figure out why it's sick?