Five to eight years of copper and black
A healthy harlequin rasbora lives 5 to 8 years in a home aquarium, and keepers occasionally report fish going beyond that in particularly stable tanks. For a fish barely two inches long, that is a respectable span — longer than most of the livebearers it is often stocked beside, and long enough that a school bought for a first tank may still be gliding around it when the aquascape has been rebuilt twice. Their hardiness helps: harlequins tolerate a wider range of conditions than many small schooling species, provided changes come slowly.
A school's lifespan is a group project
Harlequins read safety in numbers, and their bodies respond to it. A trio kept alone tends to hide, skitter and pick at food last, living under the low-grade stress that shortens small fishes' lives; a school of eight or more spreads out, displays, and feeds with confidence. The copper colour itself is a gauge — a relaxed harlequin glows, while a stressed or ageing one washes pale. Keep the group intact as fish are lost over the years by topping up with younger stock, so the remaining seniors never drop below the numbers that make them feel secure.
Water that echoes their home streams
In the wild, harlequins live in soft, slightly acidic forest streams stained by leaf litter, and longevity at home tracks how closely the tank echoes that. They do best in water kept soft to moderately soft, gently acidic to neutral, and steady around 73 to 79°F. Stability matters more than hitting exact numbers: a harlequin that has settled into your tap water's profile will outlive one chased through constant adjustments with buffers and additives. A dark substrate, background planting and some floating cover to soften the light recreate the dim edges these fish prefer, and a dimmer tank is a calmer, longer-lived school.
Habits that carry a school to old age
Feed small and varied — a fine staple crumble one day, micro-pellets, daphnia or mosquito larvae the next — because harlequins have small mouths and do best on small meals fully eaten within a couple of minutes. Change a modest portion of water weekly rather than a large share rarely, always bringing the new water to temperature first. Quarantine new arrivals before they join the school, since a disease introduced to a settled group can undo years of good keeping in a fortnight. The danger signs in an older school are practical ones: a fish hanging apart from the group, fins clamped, or the school's colour fading across several fish at once means test the water before assuming it is age.
Those small weekly duties are exactly the kind that slip in a busy household, so KinsLe Care Teams lets you assign the school's water change and feeding checks to whoever is home, with each completed task marked by a timestamp everyone can see.