Hi. I have a 55 gal. aquarium with mostly silver dollar and angel fish. They are all at least 5 yrs old. I have a silver-dollar who has is sooooo bloated, it has doubled in size. This silver-dollar is about 8 years old. I have never seen anything like it. I have been to our pet stores and no one has ever heard of this. I would appreciate any ideas about it. Thank you.