I picked up a few hatchetfish today and noticed one has red around its pupil in one eye. It has been hiding from the others and breathing rapidly. Is this something I should be worried about or will it go away on its own?
Could be an injury that will heal on its own, could be an infection, an eye fluke there are several possibilities. It's hard to say without seeing it, even then it might be hard to say. A very clear close up picture would help.