Betta not eating
 

Ive had Sushi (my betta) for about a year and lately he hasn't been eating much. About one pellet every two or three days and ignores bloodworms which worries me because he used to eat four pellets a day just fine. The weirdest thing is although he hasnt been eating for the last few weeks, his belly is still slightly convex and hes still making bubbles normally. In fact he seems completely healthy but for the not eating.

Is this normal? Like some kind of winter torpor? The tank is 1.5gal with a plant, gravel, small lamp (light and heat). The temperature is kept pretty constant at about 19deg C (which is what it was before he stopped eating).