Apart from odinium this is the only type of illness which I have observed also with paros. I have observed it mainly in females (and at least on one occasion) it was following a time of spawning.
I have been thinking also in terms of swimbladder problems without being able to say much more about it than that. I have seen fish live long time with it, – but I do not think the prognosis is all that good.
I might have raised the temperature a little, – 27,28 C for a time.
Other times I have experienced it when I have received a bigger import (25) fishes, – and took it as strain, stress