My girlfriend has several fish that have recently died. All of them were shaking their entire bodies around back and forth for some time before they died.
Any ideas why?
It’s gotta be something bad in the water. First, most obvious question: is your gal using the proper amount of de-chlorinator? If the answer is yes, I found the next biggest problem was ammonia in the water, which can be fixed by tossing in an anti-ammonia rock. After that, it could be parasites, bacteria, other chemicals, or evil housemates. (One unintentionally evil thing I discovered my housemate’s girlfriend doing was spaying window cleaner directly onto the outside of the fish tank while compulsively cleaning. Some of it must have been misting into the tank.)
Whenever I had a case of bad water or disease I’d usually off-load the fish and change out the entire tank, leaving out everything including gravel and fake plants, then I’d slowly add things back while keeping some cheap, less-than-hardy fish in there as coalmine canaries. Neons seemed to work best. I never found an identifiable factor other than the window cleaner, though.