Clown Killifish Care: Tank Size, Diet and Tank Mates

A clown killifish tank is a surface, not a volume. The fish spend their lives in the top 15 cm of water, and wild fish turn up in streams less than 2.5 cm deep. Every rule below follows from that surface, from the lid and the footprint to still water, floating food and tank mates that stay below it.

The species is Epiplatys annulatus, also sold as the rocket killifish. Success depends on two things, food at the surface and water that stays stable.

Seven checks before buying clown killifish

Clown killifish suit a small tank only when all seven conditions hold.

1. The lid is tight, or the water sits 3 to 5 cm below an open rim.
2. The footprint is at least 45 x 30 cm for a group, or 20 litres for a trio (5 gallon stocking).
3. The surface stays still, with a sponge filter and no strong outflow.
4. Tiny live or frozen food reaches the surface daily, at least for the first month.
5. The water is soft, GH 8 °dH or lower, or blended with RO or rain water.
6. Every tank mate is small and slow at feeding time.
7. The room stays below 27°C in summer, or a cooling plan exists.

One failed check means a different fish, or a change to the tank first.

Where clown killifish come from

Clown killifish live in coastal swamps and slow streams from Guinea through Sierra Leone to Monrovia in Liberia. In February 1976, collectors measured five Sierra Leone sites where the species was caught. The readings were pH 6.3 to 6.7, hardness 1 to 2 °dH and water at 24 to 28°C. Several sites lay open to the sun, edged with water lilies and Crinum natans.

Larger killifish share these waters and prey on clown killifish. Epiplatys fasciolatus and E. bifasciatus hunt the open water, so clown killifish live in marginal weeds too dense for the bigger fish to enter. Dense floating plants in the aquarium copy that refuge.

The name annulatus means ringed, after the four black bars. It has nothing to do with annual killifish, and the species lives for years. Pseudepiplatys, the old genus name, now survives only as a subgenus.

Tank size: measure the footprint

The fish rarely go deeper than 12 to 15 cm, so surface area sets the stocking. A 45 x 30 cm footprint holds a group of 6 to 10. A 20-litre tank holds a pair or a trio.

Height adds little. The same 45 x 30 cm base holds 27 litres at 20 cm deep and 41 litres at 30 cm, so a taller tank adds water the fish never use. Long, low tanks suit the species, and keepers report good results in tanks no taller than 35 cm.

Lid and jump risk

Clown killifish jump, and they find the one gap left open. Keepers find them dried behind the tank after jumps through cord holes, filter cut-outs and lids left open during water changes. One fish cleared the rim of a jar filled only two-thirds full.

The bright spot on top of the head explains the startle. In Epiplatys, it sits over the pineal organ, which senses changes in light from above. A hand over the tank reads as a predator. Settled fish swim up to a face at the front glass but bolt at movement overhead.

Close every route out:

• Seal cord and tubing holes with filter floss, foam strip or plastic wrap.
• Fit a mesh lid over floating plants, since frogbit sulks under glass.
• Lower the water 2 to 5 cm below the rim.
• Cover most of the surface with floating plants.
• Close the lid straight after feeding and after every water change.

Hang-on-back filters need a guard at the inflow, where keepers report jumps.

Water: temperature, pH and hardness

Heat is the hard limit. In June 2026, one night at 30°C killed an entire group of clown killifish in a 70-litre tank. A breeder in Singapore logged poor egg production at 28°C and above. No measured wild site exceeded 28°C.

During a heat wave, change small amounts of cooler water and float a frozen bottle of water. Run a fan across a mesh-covered top and add an air stone, since warm water holds less oxygen.

A heater is needed when the room drops below 22°C. Forum claims of longer lives in cool, unheated tanks repeat widely, but nobody has measured them.

Hard water fades the colour and stops most breeding. German keepers report fading above GH 5. Captive-bred fish survive water up to 15 °dH, but breed poorly in it. Blend RO or rain water with hard tap water, and match every water change to the tank in temperature and hardness. Leaf litter and alder cones add tannins without peat.

Flow, plants and light

Keep the water still. An air-driven sponge filter on low is enough. A fish hanging in the middle or lower water means the flow is too strong.

Floating plants carry the setup. Frogbit, red root floater, Salvinia, water sprite and Riccia hold the eggs in their roots and hide the fry. Java moss, Anubias and Bolbitis grow in the shade below.

Dim light shows the best colour. Under bright, open light the fish look washed out and stay nervous. A dark substrate helps.

Group size, males and behaviour

Adults do not school. In the wild, one dominant male ranks above loose groups of females and juveniles. In the aquarium, each adult claims a spot under the surface.

Reference profiles say males rarely harm each other. In home tanks, keepers report subordinate males left spinning after fights and females with torn fins. Females fight as well, and a well-fed female can rule the tank.

• Keep at least 3 females per male.
• Keep no more than 2 males in a 45 cm tank.
• Break sightlines with floating plants and tall stems.
• Remove the bully or the victim at the first torn fin.

Settled fish are bold, and many wait at the surface when the lid opens.

Diet and feeding

Clown killifish are ambush feeders. They hang under the surface and strike at insects that land on it. Food that sinks past 10 to 15 cm is mostly ignored and feeds the shrimp instead.

• Live: wingless fruit flies, baby brine shrimp, Daphnia, Moina, vinegar eels and grindal worms
• Frozen: baby brine shrimp, Daphnia and Cyclops
• Dry: finely crushed flake and floating micro foods

A 2008 TFH article by breeder Mike Hellweg says the fish ignore flake completely. That described wild-derived stock. Much of the trade is now bred in Southeast Asia, and most captive-bred fish take dry food, but not on day one.

Expect 3 to 7 days of little eating after arrival, then 2 to 4 weeks of weaning. Start with live baby brine shrimp, then mix in crushed flake until the flake goes alone. A minority never switch and stay on live food.

Most refusals come down to particle size. The smallest nano pellets are often still too big, so crush flake fine and choose foods that float. Feed small amounts once or twice a day, in several spots, since the dominant male guards one.

Clown killifish tank mates

Good tank mates are small, suit soft water and leave the surface alone at feeding time. Clown killifish starve when faster fish take the food first. One pair in a UK breeder report wasted away within months in a community tank, outpaced for every live food.

Adult cherry, Amano and Caridina shrimp are safe. Shrimplets get eaten, though dense moss keeps a colony going. Shrimp and snails eat killifish eggs, so they stop most breeding.

Clown killifish also eat the fry of other species, so a community tank with them raises no fry at all.

Buying clown killifish

Online orders often arrive all male or all female. Shops sell juveniles at about 1.2 cm, before the colour shows, and males outsell females. Buy 6 or more unsexed juveniles, or sexed adults at a fish club auction. Young males show the outline of the red tail extension first, at about 1.3 cm.

Most losses come in the first 2 to 4 weeks after purchase. Quarantine new fish for 2 weeks, match the seller’s water and add a few at a time. Keeper reports do not mention velvet in this species. The documented killers are shipping stress, sudden change and crowding.

Expect about £4 each in the UK and $9 to $12 in the USA.

Breeding clown killifish

Breeding happens on its own in a dense tank without snails or shrimp. Pairs spawn nearly every day, a few eggs at a time, in floating plant roots, Java moss or wool mops. The eggs hatch in 8 to 12 days at 22 to 25°C.

Adults leave their fry alone. Older fry eat younger ones, and the faster-growing males eat their sisters. Sort the fry by size, or the brood ends up male.

The eggs measure only 0.9 mm, so the fry are tiny and the first food must be smaller than Paramecium. Start with green water, infusoria or rotifers. Vinegar eels come next, since they stay near the surface where the fry hunt. Baby brine shrimp follow after 1 to 2 weeks. Feed infusoria sparingly, since the excess fouls the water and kills fry. Males show colour at about 3 months and breed at 4 to 6 months.

Clown killifish FAQ

Sources

1. Eschmeyer’s Catalog of Fishes. Haplochilus annulatus species record (online version, October 2026). researcharchive.calacademy.org
2. Huber, J. H. (1979). Epiplatys annulatus technical file. Revue française d’Aquariologie, supplement 2/79. killi-data.org
3. American Killifish Association. SL 76 collecting trip, Sierra Leone (1976). aka.org
4. DKG Epiplatys Work Group. Introduction to Epiplatys (English translation). aka.org
5. Hellweg, M. (2008). The Clown of Killies: Epiplatys annulatus. TFH Magazine. www.tfhmagazine.com
6. Seriously Fish. Epiplatys annulatus (revised 2026). www.seriouslyfish.com
7. Aquarium Glaser. Pseudepiplatys annulatus (2009). www.aquariumglaser.de
8. IUCN Red List. Epiplatys annulatus, Least Concern (2020). www.iucnredlist.org
9. killi.co.uk. Pseudoepiplatys annulatus breeder reports. www.killi.co.uk
10. r/Aquariums. Heatwave killed all of my clown killifish (June 2026). www.reddit.com