Distended belly

[bullshark]

Greetings all, I have an 8 inch Honeycomb Grouper that I have had for over 3 years. He is a voracious eater, very bold and never hides or shys away. Always at the front glass, ready to play! I try not to feed him all the time, as I dont want a 3 foot gruoper. His belly has become VERY distended, huge like. He has been eating dried krill mostly and when I fed him some frozen shrimp and clams that come in the cubes, his belly got really big. I did not feed him for a while to see if it would go down. I did not over the course of 2 weeks. I fed him a small piece of krill which he was more than willing to chow down, dispite his huge stomach. The next day after feeding a small piece of krill the distended belly was gone?!?!? So I figured he was impacted a bit. Everything was cool for a few days, then the distended belly came back. This leads me to believe he has an infection. My question: Marycin Two? What do I use to treat this fish. I have never had to medicate this guy. Has the food gone bad? It has been in the freezer a while......
Any/All comments/recomendations!!
Thanks.

 

[bullshark]

Thanks Terry, This fish is fed small amounts a couple of times a week for the past 3 years. Everything has been fine till now. I will get some fresh food and see if he gets better, if not the the Maracyn will have to be used.

 

[bullshark]

Terry, thanks for the help. The 8 inch Honeycomb is looking much better after a meal of live ghost shrimp. I will wait another day or two than feed him some fresh clams or shrimp from the local fresh fish store. His tankmate is a 9 1/2 inch grouper of undetermined species and is doing great as well. Gonna order some garlic stuff from saltwaterfish.com to soak it in just for the added vitamins and immune system boost.
I had been feeding frozen clams and frozen krill (the kind that comes in the little cubes) that possibly went bad after too long and caused the internal infection in the grouper.