Sail fin is sick Need help

I have had a 150 gallon tank for 9 years and had sail fin for 8 years. I feed him by hand all the time. For the last 2 weeks i have noticed some changes where he is not so eager to eat alot but he did it some last night. But tonight when the lights came on he was breathing hard and sitting on the bottom some. After about 30 minutes with the lights on he began to swim around fine but you can tell something is getting worse. He has no marks at all. I have a foxface and hippo that are just as old as he is. His belly does look a little sunken or maybe pulled in like it could be empty. He usually is a very thick fish. No unusual fights except for the norm cometing for food and sometimes space. I did lose a shrimp a month ago it was about 2 years old. In the process of doing a bigger water change to see if it can save hi. But stays in corners and behind rocks most of the time. When i turn the lights of he wants to lay on bottom of tank like when he lights first cameon tonight. What can i do any help please. I did a water change frida before xmas. Dont really know have had most of my fish except 2 for over 7 years. Any ideas please help soon.

 

Sorry to hear about the issues with your fish. You have had them along time and it really has to be disappointing.

Nothing really jumps out, but really need all the parameter of the water that you can provide.

Also what are you feeding and how often?

 

Welcome to 3Reef. I wish it were under better circumstances.

When he goes to the bathroom, is the waste stringy or sometimes hang on for a bit?