Change the mix, not the whole meal
A betta moves onto a new diet safely when the bowl changes by fractions, because both his gut and his habits are built around the food he knows. Start with a meal that is mostly his current pellets with just a few of the new ones among them. Hold that mix for two or three days, then shift the balance — a little less of the old, a little more of the new — and hold again. Over about a week to ten days the new food takes over completely. A betta switched overnight may refuse the unfamiliar pellets outright or bolt them and then show digestive upset; the staged mix lets his system adjust to different ingredients and lets his brain file the new shape and smell under 'food' before it is all he is offered.
Feed pellet by pellet so nothing is faked
During the changeover, feed a betta one pellet at a time and watch each one go down. Bettas are expert at taking food in, mouthing it, and spitting it out when the texture displeases them, and a spat pellet sinks and vanishes into the gravel where it looks exactly like an eaten one. Dropping the whole meal in at once hides that rejection until the fish is suddenly 'off his food' days later. Pellet-by-pellet feeding also keeps the portion honest at a few pellets per meal, and any new pellet refused twice in a row tells you to slow the ratio down rather than push the schedule.
Read his digestion while the ratios shift
The signs that a betta's changeover is running too fast appear at both ends of the fish. Watch for meals refused that he would normally attack, new food spat out after the first days went well, long pale or stringy waste, a belly that stays rounded for hours after a small meal, and unusual lethargy between feeds. Any of these means hold the current mix for several more days instead of advancing it — the calendar serves the fish, not the other way round. A weekly fasting day still applies during the transition and gives his gut a clear run; resume the staged mix the day after rather than doubling a meal to compensate.
Handle the stubborn betta without starving him into it
Some bettas fix on one food and treat the replacement as debris, and the fix is patience plus familiarity tricks rather than hunger. Soak new pellets briefly in tank water so they soften and carry a familiar smell, and offer them first in the meal, when his appetite is keenest, followed by the old food so the sitting always ends in success. Alternate days — mostly old food one day, the new mix the next — can move a holdout that a daily creep cannot. Never let a healthy betta's refusal stretch into many days of eating nothing while you wait him out; if he will take only the old food after a genuine, gradual effort, feed him the old food and try a different new food later.
Keep variety in the finished diet
Once the betta is fully on the new staple, the changeover is not the end of the story. A diet of a single pellet, however good, is narrower than what a betta thrives on, so rotate in suitable frozen or live treats on some days and keep the weekly fast. Note which foods he takes eagerly and which he spits, because that record is gold the next time you change brands or a shop discontinues his staple. When several people feed him, that record matters even more: KinsLe Care Teams hold your betta's changeover as staged daily duties — today's mix, today's feeder, marked done with a timestamp — so the gradual plan survives busy evenings and helpful relatives.