Clown killifish

Quick facts

Adult size

3.5 cm

Lifespan

can live up to 4 years; atypical for killifish; most killis live 1-2 years, clowns are longer-lived

Tank zone

top

Temperament

peaceful

Difficulty

intermediate

Schooling

recommended 8+ (critical minimum 5, thrives at 12+)

Typically wild-caught

yes - acclimate slowly

Water parameters

Temperature

22–26°C

pH

4.0 to 7.0

Hardness

1 to 8 dGH

Tank requirements

Minimum volume

38 L

Minimum length

45 cm

Flow

low

Lighting

dim preferred

Substrate

any

Hiding spots

needed

Lid

required - jumper

Feeding

Diet: carnivore, feeds primarily at the top.

Surface feeder with a tiny upturned mouth. Live food is strongly preferred: fruit flies (Drosophila, both wingless and flightless varieties), baby brine shrimp, and mosquito larvae. Frozen food is accepted (frozen daphnia, frozen cyclops, frozen baby brine shrimp) but with less enthusiasm. Dry food (crushed flake, micro pellets) is taken reluctantly and some individuals refuse it entirely. The fish feeds by picking items off the surface film, so food must float. Sinking food is ignored. Feed twice daily in small amounts. In tanks without live food, frozen food dropped onto the surface works, but a colony of wingless fruit flies is the best long-term feeding solution for this species.

Live food required, will not accept dry or frozen alone.

Compatibility

• Tiny surface-dwelling killifish that occupies the top centimeter of the water column. At 3–3.5 cm adult size, tankmate selection is limited to other nano species.
• Pairs well with bottom-dwellers and midwater nano fish that don't compete at the surface: pygmy corys, ember tetras, chili rasboras, and shrimp. Avoid surface-feeding species that would outcompete them.
• Males are territorial toward other males at the surface. In a 20-liter tank, one male is the limit. In 40 L with dense floating plants, two males can coexist if sightlines are broken.
• The flame-pattern caudal fin on males is the visual selling point. In a nano tank with dark water and floating plants, a pair hovering at the surface is striking.

Habitat

Native to coastal West Africa: Guinea, Sierra Leone, and Liberia. Found in very shallow, slow-moving to still water in forest swamps, rice paddies, and roadside ditches. The water is soft, acidic, and heavily stained with tannins. Habitat pools are often only a few centimeters deep with dense floating vegetation (salvinia, duckweed, water lettuce). The species (Epiplatys annulatus) was described by Boulenger in 1915. The common name refers to the four vertical black bars on the body, which give a vaguely clown-like pattern. Males have a spectacular caudal fin: a flame-shaped tail with bands of blue, red, and yellow. Females have a plain rounded tail and duller body coloring. Adult size is 3–3.5 cm. The species has been available in the killifish hobby for decades but only reached the general aquarium trade more recently as nano fishkeeping gained popularity. Both wild-caught and tank-bred specimens circulate in the hobby. Unlike many killifish, clown killis are not annual species; they don't die after one season and don't require dried peat for egg storage.

Breeding

Surface spawner that deposits eggs among floating plant roots, especially salvinia, water lettuce, or floating hornwort. A pair produces a few eggs daily rather than spawning in a single large event. Eggs are attached to plant roots by short threads. Adults eat eggs and fry when they find them, so dense floating plant cover increases survival. In a species tank with heavy floating plants, fry appear on their own without intervention. For dedicated breeding, remove floating plant clumps with visible eggs every few days and transfer to a shallow hatching container with aged tank water. Eggs hatch in 10-14 days at 24°C. Fry are tiny but can take baby brine shrimp nauplii from day one, which is unusual for a fish this small and makes rearing easier than many nano species. Growth is slow; juvenile coloration appears at about 8 weeks. The species breeds readily once established in a mature tank with appropriate conditions.

Common problems

Sensitivity to water quality in small tanks is the primary concern. Clown killis are often kept in nano tanks (10–20 L) where parameter stability is harder to maintain. Small water volume means ammonia spikes from overfeeding or a dead snail can be lethal quickly. Frequent small water changes (10-15% every few days) are safer than large weekly changes. Jumping is a hazard; a tight lid is mandatory, with no gaps around tubing or filter equipment. The species doesn't tolerate strong current; use a gentle sponge filter or heavily baffled output. Feeding is the other challenge: clown killis that refuse dry food need a consistent supply of live or frozen food, which is more effort than most community fish require. Without live food, some individuals gradually waste away despite food being available.

Bioload

Bioload coefficient: 0.4 (tiny surface-dweller; load comparable to a chili rasbora).

Bioload coefficients are calibrated against the neon tetra as the anchor (1.0). See the methodology page for the formula and how each value was derived.

Further reading

• How to cycle a fish tank
• Stocking ideas by tank size