Schlesers Longfin Killifish Care Guide - Aquarium Setup, Diet & Breeding

Schlesers Longfin Killifish are striking annual killifish with an elongated body, extended finnage and an especially elegant appearance in mature males. Males typically show stronger colour, with iridescent blue or green tones, warm red markings and boldly patterned fins, while females are smaller and comparatively subdued in colour.

This species has a calm but purposeful character. Males may display and spar with one another, particularly around spawning sites, but these interactions are usually brief when the aquarium offers plenty of visual breaks and cover. They are not schooling fish, although they are engaging to watch when kept as a small breeding group.

In the wild, Schlesers Longfin Killifish inhabit shallow seasonal pools and flooded depressions in the Amazonian lowlands. These waters can be soft, acidic and stained by leaf litter and decaying vegetation, with fluctuating water levels shaping the species' unusual reproductive cycle.

Like other annual killifish, their eggs survive the dry phase rather than the adult fish. The embryos develop slowly in damp substrate and hatch when the seasonal pool is refilled. This adaptation gives the species a naturally brief adult lifespan but an extraordinarily interesting life history for aquarists.

Schlesers Longfin Killifish originate from seasonal freshwater habitats in the western Amazon region of northeastern Peru, South America. They are associated with shallow pools and temporary waters that expand during the rainy season and may dry out periodically.

A pair or small breeding group should be given at least 40 litres, with a footprint of roughly 60 by 30 cm preferred over a tall aquarium. Use a tight-fitting lid because killifish are capable jumpers. Provide subdued lighting, floating plants, fine dark sand or a soft peat-based spawning area, and dense planting or clumps of moss that create shelter and visual barriers. Gentle filtration and some leaf litter help reproduce the quiet, tannin-stained character of their seasonal habitat.

Males reach approximately 7 cm (2.8 inches) in total length, while females are usually smaller at around 5 cm (2.0 inches).

Offer a varied carnivorous diet based on appropriately sized live and frozen foods. Suitable choices include small live or frozen brine shrimp, daphnia, mosquito larvae, bloodworm and other aquatic invertebrates. They may accept quality small pellets or flakes, but regular inclusion of live or frozen foods helps maintain condition, colour and breeding performance.

Schlesers Longfin Killifish are best kept in a species aquarium or with other very peaceful, similarly sized soft-water fish. Small pencilfish, peaceful tetras, dwarf rasboras and small Corydoras may work in a spacious, mature setup, provided they do not outcompete the killifish at feeding time. Avoid fin-nipping species, boisterous fish, large cichlids and other aggressive tankmates; males can also become stressed by constant competition from more assertive fish.

Schlesers Longfin Killifish are annual spawners that deposit their eggs into soft peat, fine sand or a spawning mop. Keep a male with two or more females to spread courtship pressure, and remove the spawning material regularly. The eggs require a period of dormancy, usually several months, before being returned to shallow, clean water to hatch. Newly hatched fry accept infusoria or other tiny first foods before progressing to microworms and newly hatched brine shrimp.

Males are larger and much more colourful, with elongated dorsal, anal and caudal fins that give the species its longfin appearance. Females are smaller, deeper-bodied and generally brownish or grey with shorter, less ornate fins.