Why is my betta floating?

Brief：
He appears totally healthy. However, whenever I feed him (3 pellets), he suddenly becomes bouyant, like a bobber. This lasts about 12 hours or so. Ive.. 

He appears totally healthy. However, whenever I feed him (3 pellets), he suddenly becomes bouyant, like a bobber. This lasts about 12 hours or so. I've had him for 4 months, and this just started a week ago.do you know what is going on?

from www.Bettatalk.com

DISEASE: SWIM BLADDER DISORDER

uGENERAL INFO:

This is also a common betta problem. It is not contagious. It comes from overfeeding. It is especially common in very young bettas (30 to 60 days old) and can affect some Double Tail bettas when overfed or stressed..

uSYMPTOMS:

Bettas with a swim bladder disorder will have difficulty swimming, because their swim bladder (located alongside the spine between the belly and the tail) is either too short (causing them to not be able to swim horizontally) or it is swollen (causing them to float on one side). Double Tail bettas, because they have a shorter body, are especially prone to the “floaters” problem. In the case of a short swim bladder, the bettas will not be able to maneuver and swimming becomes so difficult, they prefer to just lay at the bottom, sliding on their bellies, which is why they are called “belly sliders”. And they do look like a pathetic bunch, at that point. :)

uTREATMENT:

Bettas may recover on their own, but since overfeeding induces swimbladder disorders in most cases, the first thing to do is feed a lot less. Brine shrimp and too much of it is the biggest culprit, so if your bettas are bellysliding, stop the brine shrimp for a while and thereafter learn to have a more balanced diet, alternating brine shrimp with microworms or worms (depending on how old your bettas are). Do not kill a betta with a swimbladder disorder. It may recover on its own at any time, and is not suffering. Further more, the ailment is NOT contagious. To help the fish if it cannot eat, lower the water level. Adding some BettaZing to the water for a few weeks may not hurt either ;). I'm sorry I've never heard of this one ..Iknow that they bob like that when they sleep but to sleep that much!? I dn't think thats the problem. And 3 pellets doesn't seem to be a whole lot of food for him. juz my opinion very old for a betta my betta lasted about 5 months yes you feed him pellets, let me guess the are the flotting kind!they can be hard to brake down so feed him flakes or soak the pellets in a cup of water untill they get mussy then feed you fish. he will then no longer have gass I would consult your local pet store or vet. It could be serious! because its hungry I have 10 bettas I feed them the flakes and all of them has done better with that then the pellets. When I fed them pellets they did that a lot and it worried me. So my advice get him flakes. Also they do sleep like that too. Bettas will live for 3-5 years, and are generally .5-1 years old when you buy them. He might have a mild case of swim bladder disorder. It's not a lethal condition, but it could be a sign of a more serious condition. You might try giving him a day of fasting, and feed him a pealed cooked pea. Also be sure you are changing his water regularly. Lastly try 1 teaspoon of table salt per 2.5 gallons.