Around 4 months ago, I received a trio of banded darter from a friend. These bandeds only accept blood worms, I've been training them since but to no avail, they ignore frozen brine shrimp, frozen mysis shrimp, fully chopped shrimp meat...
So far I feed them once a day, and twice on weekends. They've been doing OK until last week I noticed their belly is becoming very flat, flatter than before, and even looks a little bit sunken. They are still eating well, get rounded belly during every feeding time, but next day they will look entirely flat again.
I don't think it's a normal sign, healthy fish will be plump.
Maybe it is bad food quality? Or water temp is too high? it's almost 80f in the tank. Or internal parasites?
These pics are taken in healthy days...