What changes inside the school at feeding
An aging harlequin rasbora feeds like a guest at a meal it used to host. In a healthy school the whole group boils up to the surface together when food lands, each fish snatching flakes in rapid turns, but the oldest rasboras rise a fraction later, take a few pieces, and sink back to midwater while the younger fish are still competing overhead. Their midwater cruising slows too; an old harlequin holds a steadier position in the school instead of constantly reshuffling within it. Nothing about this looks dramatic on any single day, which is exactly why harlequins lose condition unnoticed — the school still feeds noisily, just with fewer mouths truly fed.
Why an old rasbora's profile slims
A harlequin rasbora's deep, laterally compressed body makes weight change easy to read once you know where to look. The area in front of the black wedge should be filled and gently curved; in a thinning senior that curve flattens, the belly line pulls up, and the fish starts to look triangular in the wrong way — head-heavy and narrow behind. Muscle loss along the back contributes as much as fat loss, because old rasboras simply swim less distance each day. The copper and rose tones mute as condition drops, though colour alone misleads, since lighting and mood shift it hourly; trust the silhouette over the shade.
Feeding the edge of the school
Spread food for an aging harlequin rasbora across the whole surface rather than dropping it in one rich spot. A wide scatter of fine flake and slow-sinking micro-granules lets an old fish feed at the school's shoulder, picking off drifting pieces without entering the centre scrum. Feed the main ration, wait a few minutes, then add a small second sprinkle aimed at the quieter end of the tank where the seniors regroup. Keep flow gentle at the surface so food lingers where a slower rasbora can reach it instead of being swept to the filter before its second rise.
Reading the wedge, silhouette and colour
Use the dark wedge on an aging harlequin rasbora as your measuring frame. On a fish holding weight, the body ahead of that wedge stays deep and the wedge's edges look clean against filled flanks; on a thinning fish the same wedge seems to occupy more of a shrinking body. Compare individuals side by side during the calm after feeding, when the school hangs in a row and silhouettes are easy to rank. Note also which fish repeatedly end a feeding at the back — a rasbora that is last up and first down three feedings running is the one to watch, whatever its silhouette says today.
When a quiet feeder needs investigation
An aging harlequin rasbora that stops rising with the school, hangs alone near the plants, or shows a pinched belly with a knife-thin back needs advice from an aquatic vet or experienced fish-health specialist. If several rasboras slim together, test the water first and record the numbers, because a school-wide change is a tank story until proven otherwise. Write down how the group's feeding boil has changed — weaker, shorter, missing members — since that behaviour summary often points an advisor toward the cause faster than a description of one fish. Filing the water results, silhouette notes and feeding observations in KinsLe's Pet Passport keeps the whole school's history ready in one place.