Two days ago I brought my new friend home and moved him from his dirty plastic cup into a 3.5g tank with a heater and a low-flow filter. I've been keeping a close eye on toxin levels while the tank cycles; I do testing twice daily and my policy is a 25-50% water change any time ammonia reads above 0.25ppm, with use of Prime to mitigate any harm in the meantime.

Since entering his new home, my little buddy has gone from obviously stressed (fins clamped, lethargic, skittish) to reasonably at peace (fins relaxed and billowing, exploring, inquisitive), but he still won't eat any pellets I drop in the tank. On the first day he chomped one down only to spit it back out a moment later, and since then he has had no interest in them.

I know that betta fish can be picky eaters and from what I read it's relatively common for them to refuse food for a while upon arrival in a new tank, but I'm still worried. The poor little guys stomach almost looks concave. Is this just a phase I can expect to pass soon, or should I try to get more enticing food like live worms to get the little guy to eat before he starves?