A betta breathes air at the surface and eats at the surface, so an old fish who tires on the swim up pays for every breath and every meal with the same hard climb. Bettas often live around two to four years, and in that later stretch the useful changes shorten the journey rather than urging the fish to try harder.
Placing rests he can actually use
Set up the resting places first, before touching flow or water level. Anchor broad leaves so the leaf blade sits a centimetre or two below the surface, flat enough for him to lie across without gripping. Add a floating log that drifts little and a shallow resting shelf fixed to the glass near the top, then spread the three rests around the tank so a perch sits near each spot where he settles during the day. A rest placed only beside the filter does him little good if he spends his afternoons at the opposite end. Watch where he chooses to sleep for two evenings, because his chosen corner tells you where the next rest belongs. Leaves with rough edges or sharp plastic stems can tear ageing fins, so run a fingertip over every edge before a rest goes in.
Gentler flow and a slightly lower surface
Strong filter flow taxes a senior betta twice, pushing him off his rests and making the surface itself hard to hold position on. Baffle the filter output or turn the flow down where the filter allows it, and aim the current along the back glass so open water near his rests stays calmer. Lowering the water level a little shortens the climb from mid-water, and even a small drop helps a fish who rests often. Lower it only while the filter intake stays submerged and the heater keeps its required coverage, and mark the new level on the glass so a water change restores the same depth each time. Make one change at a time across several days, so you can see which adjustment actually helped him.
Feeding above his perch
Feed him at the perch he uses around feeding time, dropping one piece at a time directly above him so he rises a short distance, takes it, and settles again. Small pieces he can manage in one bite save repeated trips, and removing uneaten pieces after a few minutes keeps the surface film and water clean for a fish who spends his life near both. If food drifts, still the surface briefly by pausing the filter during the feed where your setup allows that safely, then restart it straight afterwards. Note which perch he feeds from, because a fish who changes his feeding perch may be telling you the old spot has become harder to reach.
Watching for change that needs more help
Easy surface access should make his days visibly calmer within a week or so. Seek advice from an aquatic vet if he still cannot reach the surface without distress, gasps at the top, stops feeding, or lies on his side between rests, because those signs can reflect problems a vet needs to investigate rather than age alone. Test the water first in every case, since an old fish shows slipping conditions early and clean, warm, stable water may ease the effort while you arrange advice.
As his needs shift again, KinsLe's Pet Passport lets you keep a dated note of the perch layout, water level and feeding spot that suit him, ready to share with anyone covering his care.