Weak Snick

I have a theee year old male seahorse hat came from a very dirty tank and seems unable to suck in his food. He tries, gets exited to eat and then just nods his head at the food. I came across a reply to this problem where you told her that it’s either from an injury or lodged object or some sort of parasite. His breathing does seem labored and I’m worried he’s for some sort of parasite. My question is, how do I identify what it is and how to treat it?