Why an older betta leaves food behind
A senior betta's smaller appetite is usually a pace problem before it is a quantity problem. His metabolism has slowed, his eyesight and aim are not what they were, and pellets that drift or sink quickly can be missed entirely, even by a fish who is still hungry. He may also tire partway through a meal he once finished eagerly: a few mouthfuls, a rest on a leaf near the surface, and by the time he returns the rest of the food is waterlogged on the substrate. Read the leftovers as information — he is telling you the meal shape no longer fits him, not that he needs less food overall.
Smaller meals, more often
Split his old ration into two or three small feedings spread across the day: morning, midday if someone is home, and evening. Each feeding should be only what he eats in roughly a minute of active feeding; count out a few pellets rather than scattering a pinch, because a known number lets you notice when intake drops further. Small and often suits his slower digestion better than one large load, and it keeps his energy steadier than a single meal followed by a long fast. If your household keeps irregular hours, anchor the feedings to events that always happen — lights on, your own evening meal — rather than to clock times nobody can keep.
Making each small meal count
Pre-soak pellets in a little tank water for a few minutes so they soften and sink slowly; a senior betta takes softened food far more reliably than hard pellets that bounce off the surface film. Offer food in the same quiet corner each time, away from the filter outflow, and use a floating feeding ring if stray pellets drifting off are part of the problem. On some days, swap one pellet feeding for a soft, protein-rich food he has always liked, served in tiny amounts — variety often revives interest in a fish who has gone lukewarm on his staple. Feed at the surface where he rests; an old betta should not have to chase food down through the water column.
Keeping the water clean between meals
More feedings means more chances to pollute a small tank, so remove anything uneaten within a few minutes of each meal, using a small net or a baster kept only for the tank. Test a senior betta's water a little more often than a young fish's, because his tolerance for slipping quality is lower and the extra feedings add load. Keep up his regular partial water changes on schedule — stability matters more to him than chasing perfect numbers with big, disruptive changes.
When reduced appetite needs a vet
A gradual shrinking of meals is common in old age; a sudden stop is not. Contact an aquatic vet if he refuses food entirely for more than a couple of days, if he loses visible body condition along the back and belly, develops raised scales, clamped fins or pale patches, or starts gasping or lying on the bottom unable to rise for food. Note when the change began and what he last ate well — that history helps the vet far more than a general report that he is off his food.
Splitting his day into several small feedings takes coordination, and KinsLe's Care Teams lets each feeding be assigned to a named person and marked complete with a timestamp, so everyone in the house can see he has eaten.