Breathing only on one side

[ek]

My Queen angel is breathing only from one gill the other one is shut tight. He is swimming and eating but opening that closed gill only to the cleaner wrasse. What is this?

 

[fishymissy]

Gill flukes.
If the wrasse is cleaning that gill, I wouldn't remove the fish just yet. If the fish stops eating or seems to have trouble breathing, you will need to remove it to a hospital tank to treat. Then you would have to use a medication to rid the fish of external parasites. (Not internal).
HTH