I've had my male betta a month shy of 3 years. He's been incredibly lethargic since new year's weekend. He is typically very active and spends the day swimming energetically around his tank. For the past 2 weeks however, he just lays at the bottom of his tank. He only comes up for air and feedings. He used to follow my finger on the outside of his tank and jump if I put it above his water, but has stopped doing both.

He's in a filtered 10 gal tank with a heater. His water is 82F. I do regular water changes and monitor it for PH, ammonia and nitrates...water wise, his tank is fine. I even took a water sample to our local pet store for testing, since their kits are a bit more elaborate & they agreed that his water is fine. Their fish expert chalked it up to "old age." But his personality changed overnight, so I'm really worried that he's suffering.

He's a pale yellow, translucent betta, but he looks even paler than normal. Other than that, he looks perfectly fine. His fins still look great & he hasn't lost his appetite at all. Is it possible that he is just bored? I've never added any other fish to his tank because he's always been so aggressive.

Any help at all is really appreciated!!