Have you changed his diet recently? sometimes they are picky eaters.
My old beta started to act this way once he was really old...perhaps it could be old age 4 years is a long time for a betta to live.
but you should check to see if there are any other signs of illness so people can better diagnose the problem. Like any lesions, dull color, fin damage etc...
I forgot to add...cold water can cause them to become lethargic and have a lowered metabolism, resulting in less food consumption. If you can place the tank in the warmest area of the room or your warmest room. The water should be in the high 70's in temperature.
Last edited by JamieTron; 01-05-2010 at 06:13 PM.