Help please

[Dmusic]

My red devil, approximately 11, stopped eating after aquarium cleaning 3weeks ago. He's done this before ,after cleaning, just never this long. Also heavy breathing, and yellow stringy coming out of his butt. Enclosed is picture of the stuff.someone help me

 

[TheRisingPhoenix]

Hey sorry to hear about your fish issues. It looks like it's infection. Either bacterial or viral. When you clean the tank it certainly does stress him out which will account for not eating. Fish can go a month or more without eating so don't worry so much about that right now. You'll need to address the possible infection first. If you figure that out im sure food will be his next thought. What are your water parameters? Did you test the tank? If you didn't you'll need to or else online help is all guessing. Api makes a great master test kit it's liquid drops. I found on Amazon for $25 or under... maybe even cheaper on Ebay. Reply back with your test results.