He is a very old little fella. Their lifespan is 2-3 years. You've done a great job in caring for him all this time. I'm afraid he's at the end of his days now. Keep his as comfy as you can with regular water changes. He will be more prone to stress now that he is older so it is very important to make sure the temperature of the new water is the same as the old when you clean his tank. Put his tank in the warmest spot in your house. Heat will boost his immune system and make him feel better for now.
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http://en.allexperts.com/q/Fish-1472...sick-dying.htm
η ακόμα
He may need to be warmer. Cool water can cause constipation and then gas that can make bettas float. Put a lamp on him to get the temperature up to 80 or 82. Once he starts eating again offer him (thawed) frozen green peas broken into little chunks. Here are some sites to help you with more betta info;
η σχέση Farheneit Celsius ειναι C=-32*(5/9)F