old age and stress i can say more than that as i don't know that species and when introducing fish use a stress reducing chemical lie metaflex (metaflex is great lowers streess and fight nasty parasites and desesse.)
thanx 4 your comments........xxxx....lol@ chirpy chirpy cheep cheep. Had the fish 4 quite a while......didn't seem to be stressed and his friends are fine. Never mind....he's happy in fishy heaven.