Aristotle developed this sac around the bottom of his right eye. Anyone ever seen this? Any vets here diagnose based on these photos? He has been living alone in a 55 gallon tank for years happily but this suddenly came about.
Water always excellent and consistent
pH around 8
hardness well within goldfish range
ammonia, nitrite and nitrates all 0
diurnal light regularly
food varied Hikari and freeze dried daphnia.
Could it be some bacteria could be transmitted through the freeze dried daphnia?? i don't even know if it's an infection at all. There are no sharp edges in the aquarium, i doubt it's an injury.