Why he keeps arriving after the food has gone
A koi that surfaces slowly is usually losing the race in three ways at once. His rise from the bottom takes longer because old muscles and a stiffer body make the climb slow work. His eyes find the floating pellets later than they once did, and pond light on rippling water hides food from ageing eyes even at close range. And the younger fish in the pond are simply quicker — by the time he breaks the surface, the pellets near him have been taken or have drifted beyond his unhurried turn. He is not necessarily eating less because he wants less; he is eating less because the meal is served where speed wins.
Take part of his meal down to him
The simplest change is to split his ration. Keep floating food for the pond generally, but drop a portion of good sinking pellets in the same sheltered corner he favours — near a plant shelf, along a quiet wall, wherever he habitually rests. Sinking food waits where he lives instead of passing overhead, and he can graze it at his own pace without surfacing at all. Soaking the pellets briefly first softens them for an older mouth and makes them sink steadily rather than tumbling. Within a week or so most koi learn that corner delivers, and he will begin drifting toward it when he sees you approach the pond edge.
Give him the quiet corner and a head start
Sequence the feed so competition never reaches him. Throw the floating ration wide at the far end of the pond first and let the younger fish commit to their scramble; then walk his sinking portion to his corner and drop it in while the crowd is busy. He gets several undisturbed minutes, which is all a slow feeder needs. Resist topping up his corner repeatedly through the day to compensate — little and regular beats anxious extras, and constant food in one corner fouls the water exactly where he rests.
Hand-feeding builds on years of trust
A koi kept for many years often already associates your shadow at the pond edge with food, and that trust is worth using. Crouch at his corner, hold a few softened pellets just under the surface and wait. Many old koi will nudge up and take food from fingers once they learn the spot, and feeding by hand removes every rival from the equation while letting you see precisely how much he eats. Keep sessions calm and brief, and always at the same place — the predictability is the point, and a fish that knows where his dinner appears stops wasting energy patrolling for it.
Watch his condition across the season
Judge success on his body, not on any single feed: his sides should stay filled out, his energy steady, his resting normal rather than listless. Weigh nothing and measure nothing fancy — a honest look at him each week alongside the pond's other residents tells you whether his share is reaching him. Recording his corner routine and everyone's observations in KinsLe's Family Sharing means the family member who feeds on a weekday and the one who visits at weekends are watching the same fish in the same way, and a real decline gets noticed instead of explained away.