Clown Killifish Care Guide: The Tiny Nano Fish With Big Personality

Species Overview#

Clown killifish (Epiplatys annulatus) are one of the most striking nano fish in the freshwater hobby — a torpedo-shaped 1.3-inch surface dweller wearing four bold black bands across a pale cream body, with males flaring red, blue, and yellow lyre-shaped tails when they display. They come from the soft, tannin-stained streams of West Africa, and the moment you see a small group hovering inches below the water surface beneath a mat of floating plants, it's clear why they've earned a cult following in nano and planted-tank circles.

They are not a difficult fish, but they are a specific one. Get the tank size, lid, and water chemistry right and they live 3 to 5 years, breed in your floating plants, and put on a daily show at the surface. Skip the lid or stock them with the wrong tank mates and you'll be picking fish off the floor. This guide covers every parameter that matters for the species.

Adult size

1.25-1.5 in (3-3.5 cm)

Lifespan

3-5 years

Min tank

5 gallons

Temperament

Peaceful surface dweller

Difficulty

Beginner with a tight lid

Diet

Micro-predator

Natural Habitat#

Epiplatys annulatus lives in shallow, slow-moving blackwater streams and swamp margins across Guinea, Sierra Leone, and Liberia. The water is soft, acidic, and stained the color of weak tea by tannins from decaying leaf litter and overhanging vegetation. Visibility is short, current is barely measurable, and the substrate is a mix of leaf litter and fine sand under a dense canopy of marginal plants.

The chemistry sits at the soft end of the spectrum: pH typically reads 5.5 to 6.5, hardness rarely climbs above 4 dGH, and water temperatures hold between the high 60s and high 70s Fahrenheit depending on shade and season. These are not rivers — they are slow forest creeks and pools the fish can almost stand still in. Recreating even a softened version of this habitat in your aquarium pays off in coloration and natural surface-skimming behavior.

Appearance & Size#

Clown killifish are unmistakable once you see them. The body is a slim cream-to-buttery torpedo crossed by four vertical black bands — the trade name "rocket killifish" comes from the way the body shape and banding suggest a striped missile. The mouth is sharply upturned, designed for picking food off the surface film.

Males carry the show colors. Their lyre-shaped caudal fin flashes a central red and blue gradient flanked by yellow rays, and dominant males flush deeper color when displaying to females or competing with rival males. Females are slightly larger and rounder in the belly, with a plainer fan-shaped tail and softer banding. Adult size tops out at 1.2 to 1.4 inches (3 to 3.5 cm), making them true nano fish — smaller than most ember tetras and well under the size of a typical neon.

Lifespan & Behavior#

Well-kept clown killifish live 3 to 5 years in the home aquarium. That is long for the killifish family — many Nothobranchius and other annual killifish species complete their entire life cycle in under a year. Epiplatys annulatus is non-annual, which means they live the way most aquarium fish do, year over year, without seasonal die-offs.

Behaviorally, they are surface specialists. They hover in the top inch of the water column, often beneath floating plants, picking off mosquito larvae, springtails, and anything else that lands on the surface film. Males display constantly when females are present, flaring fins and racing each other — but actual injury is rare. This is mostly a posing-and-chasing species, not a fin-shredding one.

Water Parameters & Tank Requirements#

Get the chemistry, tank size, and lid right before the fish arrive. With a 1.3-inch fish and a tank typically measured in single-digit gallons, there is no buffer against ammonia spikes or open-top jumps.

Ideal Water Parameters#

Aim for soft, slightly acidic water in the range of pH 6.0 to 7.0 and 4 to 8 dGH hardness. Clown killifish tolerate up to about pH 7.5 if they're acclimated slowly, but they show their best color and breed most readily under the lower-pH, softer-water side of that range. A pinch of Indian almond leaf or alder cone in the tank pushes the chemistry toward their preferred blackwater profile and tints the water a tea color that suits their natural look.

Temperature should run between 68 and 79°F (20-26°C). They do not need heat — in fact, they tolerate the cool end of that range better than they tolerate sustained temperatures above 80°F. A simple 25- to 50-watt heater set to 74-76°F is plenty for a 5- to 10-gallon nano. If your house stays above 68°F year-round, many keepers run them unheated successfully.

Test your tap with a basic API GH/KH kit before you commit to a setup. If it reads above 12 dGH and pH 8.0, plan for RO water blended with tap or pick a different species — long-term success and breeding require the softer, slightly acidic side of the range.

Tank Size & Setup#

A 5-gallon tank is the practical minimum for a small group of 4 to 6 clown killifish. They are tiny, they don't move much, and they spend nearly all their time in the top inch of the water column — gallonage matters less for them than for active mid-water shoalers. A 10-gallon is the better default if you're starting fresh, and it supports a colony of 8 to 10 plus a small group of compatible nano companions.

Floating plants are not optional. Dwarf water lettuce, frogbit, salvinia, or red root floater all work — the fish need overhead cover at the surface to feel secure and to claim breeding territory. A bare-surface tank stresses them and dramatically reduces breeding behavior. Beneath the floaters, plant the tank densely with stem plants, java moss, and shaded backgrounds. Leaf litter and a piece or two of driftwood complete the blackwater look.

The Fluval Flex 9-gallon is a near-perfect off-the-shelf home for a clown killifish colony. The curved front, built-in filtration chamber, and tight-fitting hood address the two biggest setup needs in one box — surface coverage and a sealed top. With a thin mat of frogbit and a heavy planting, it looks like a slice of West African swamp on a desk.

Filtration & Flow#

A simple sponge filter run by an air pump is the right choice for a clown killifish tank. It provides gentle biological filtration, keeps surface agitation low, and poses zero risk of sucking in fry or stressing the surface-dwelling adults. A small hang-on-back filter works too if you baffle the output with a piece of pre-filter sponge or aim the flow against the back glass to break it up.

Flow should be barely perceptible. These are fish from slow forest creeks and swamp margins — strong currents push them around the tank and disrupt the calm surface they need to feed and breed. If your floating plants are getting blown across the tank, your flow is too strong. Dial it back until the floaters drift slowly or stay nearly still.

Avoid powerheads and aggressive surface skimmers. Some surface movement is fine for gas exchange — the goal is a film of slow-drifting floating plants over a calm surface, not a churned-up top.

Diet & Feeding#

Clown killifish are micro-predators with tiny, upturned mouths that key on the surface film. Feed them food they can actually fit in their mouths — and plan to lean on small live and frozen foods more than dry options.

Staple Foods#

Crushed micro-pellets and finely ground flake work as a daily backup, but only if the particle size is roughly 0.5 mm or smaller. Most standard tropical flake is too large. Brands that sell "nano" or "micro" formulations (Hikari Micro Wafers, Bug Bites Micro, NLS Small Fry) are sized appropriately when crushed between your fingers. Drop food in a pinch directly onto the floating plants so it stays at the surface where the fish are.

Be honest with yourself about dry food acceptance. Many clown killifish refuse dry food entirely, especially if they were wild-caught or recently weaned off live foods at the breeder. If yours ignore crushed flake after a few attempts, treat that as normal — they will need live or frozen foods as their primary diet, not as a treat.

Live & Frozen Enrichment#

Baby brine shrimp, microworms, banana worms, vinegar eels, and grindal worms are the gold-standard diet for this species. Daphnia, cyclops, and small wingless fruit flies all work as well. Frozen versions of brine shrimp, daphnia, and cyclops are widely available and acceptable substitutes when live cultures aren't practical.

Live food does more than just feed them. A few days of conditioning on baby brine shrimp triggers spawning behavior, deepens male coloration, and brings out the surface-strike feeding response that makes the species so entertaining. If you intend to breed clown killifish, plan to keep at least one live culture going year-round.

Feeding Frequency & Quantity#

Feed small amounts twice daily. Each feeding should be cleared from the surface within two to three minutes. The biggest mistake new keepers make is dumping a pinch of flake the way they would for tetras — most of it sinks past the killifish and rots in the substrate, fouling water quality in the small volumes these tanks usually run.

For a group of 6 to 8 fish, a single baby brine shrimp feeding the size of a pencil eraser is plenty. If food is sinking before it's eaten, use a finer grind or a food that floats longer.

Tank Mates & Compatibility#

The right tank mates are small, peaceful, and stay out of the surface zone. The wrong ones nip fins, outcompete the killifish at the surface, or simply intimidate them into hiding.

Ideal Nano Companions#

Best matches are small, peaceful nano species that occupy the lower water column or schoal in mid-water without crowding the surface. Ember tetras, chili rasboras, pygmy corydoras, Boraras species, and small Microdevario rasboras all work well. Pencilfish are another natural fit — many of them stay in the upper half of the tank but are too peaceful to harass the killifish.

Neocaridina shrimp (cherry shrimp, blue dream, etc.) coexist beautifully with adults — the shrimp recycle leftover food and the fish are too small to threaten anything but newly hatched shrimplets. Nerite snails and small bladder snails are completely safe.

Species to Avoid#

Skip anything large enough to bully or intimidate them, anything with a reputation for fin-nipping, and anything that competes for the surface. Bettas are an instant no — both species claim the top of the tank and the betta will win. Guppies and endlers are another bad match: their flowing fins trigger the male killifish's display response, and the killifish are quick enough at the surface to harass the guppies right back. Result: stress on both sides.

Also avoid fast-moving barbs, tiger barbs especially, and anything that hits the 2-inch-plus range. Angelfish, gouramis, and any cichlid larger than a Pelvicachromis will treat the killifish as snacks. Rule of thumb: if a tank mate's mouth can fit a clown killifish, it eventually will.

Keeping Groups#

Buy at least 6 clown killifish to start. They are not a tight schooling species, but they need company to display naturally — a single pair becomes shy and rarely shows full color. A male-to-female ratio of 1:2 or 1:3 spreads male display behavior across multiple females and prevents any one female from being constantly chased.

A species-only colony of 8 to 10 in a 10-gallon planted tank is one of the most rewarding setups in the nano hobby. They display constantly, breed in the floating plants, and are visually impossible to ignore against a dark, leaf-littered background.

Breeding#

Clown killifish breed readily in a well-planted tank with the right conditions. They are one of the easier killifish to breed for hobbyists because they are non-annual — eggs hatch in days, not months, and require no peat-storage protocol.

Conditioning & Spawning Triggers#

Condition adults on live foods for one to two weeks before you expect spawning — baby brine shrimp once a day will visibly fatten females and intensify male color. Raise the temperature slightly, from a baseline of 74-75°F up to 76-78°F, to push spawning behavior. Add a thick mat of floating plants (frogbit or dwarf water lettuce) or a yarn spawning mop suspended at the surface.

Males will display constantly to females in spawning condition, fanning fins and chasing them through the floating cover. Spawning happens in short bursts beneath the floaters, with the female releasing one or two eggs at a time that stick to plant roots, moss, or mop fibers.

Egg Care & Fry#

Eggs are clear, roughly 1 mm across, and hatch in 10 to 14 days at 75-78°F. The simplest approach is to pull the spawning mop or a section of floating plant into a small breeder container with tank water, an air-driven sponge filter, and a lid. Adults eat their own eggs and fry, so separation is the only reliable way to get fry to grow-out size.

Fry are extremely small at hatch — too small for baby brine shrimp in the first week. Start them on infusoria, vinegar eels, or commercial liquid fry food for the first 7 days. By week two, they can take freshly hatched baby brine shrimp, which becomes their staple until they are large enough for crushed micro-pellets.

Raising Fry to Juvenile#

Once fry accept baby brine shrimp at around two weeks, they grow steadily on twice-daily feedings. A 2- to 3-gallon dedicated grow-out tank with a thin layer of leaf litter, a sponge filter, and floating plants gives them ideal conditions. Avoid the temptation to do large water changes — small daily top-ups and 20% changes once a week are gentler on fry that small.

Juveniles reach roughly half-inch size by 8 to 10 weeks. Sexable bands show at three months; full adult color and breeding-ready size arrive around six months.

Common Health Issues#

Clown killifish are hardy when their water is right. Most of the problems keepers run into trace back to either water quality in undersized tanks or the species' particular sensitivities to a few specific issues.

Velvet (Oodinium)#

Marine and freshwater velvet (Oodinium) is the disease clown killifish are most prone to, and it kills fast. Symptoms include a fine gold or rust-colored dusting on the body and fins, scratching against decor, rapid breathing, and lethargy. Catch it early — within the first day of dusting — or losses pile up.

Treat in a quarantine tank rather than the display. Epiplatys annulatus tolerates copper poorly, so avoid copper-based velvet treatments if possible; a temperature raise to 82°F combined with daily water changes and a low-dose acriflavine or methylene blue treatment is a safer first-line option. Dim the tank during treatment — velvet has a photosynthetic life stage and slows in low light.

Bacterial Infections from Poor Water Quality#

In tanks under 10 gallons, ammonia and nitrite spikes happen fast, and they are the underlying cause of most bacterial infections in this species. Symptoms include clamped fins, frayed fin edges, faded color, and a generally hunched, listless posture.

Prevention beats treatment every time. Run a sponge filter sized one step larger than the tank suggests, do small (15-20%) water changes weekly using temperature-matched water, and never overfeed. If you do see bacterial signs, test water immediately, fix the root cause, and consider a broad-spectrum antibiotic like Furan-2 if symptoms don't improve within 48 hours of correcting water quality.

Stress & Jumping#

Stress-driven jumping is the single most common cause of death in clown killifish, full stop. Triggers include tank-mate aggression, surface turbulence from too much flow, sudden room lights flicking on at night, and the keeper's reflection passing across the tank. Cover every lid gap, run gentle flow, and consider a dim night light to reduce startle jumps in dark rooms.

A jumped fish found within a minute or two and returned to water can sometimes be saved if the gills haven't dried out — but the right move is to never give them the chance. Lid security is the highest-impact piece of equipment you'll buy for this species.

Where to Buy & What to Look For#

Clown killifish move through specialty channels more than chain stores. Where you source them matters as much as which tank you put them in.

LFS vs. Online Sources#

Local fish stores carry clown killifish inconsistently — some independent shops and aquatic plant specialists keep them regularly, while big-box chains rarely stock them. A specialty killifish breeder, a small online retailer focused on nano fish, or a member of the American Killifish Association classified board often produces healthier, better-conditioned fish than a generic importer.

The advantage of buying local, when you can, is being able to watch the fish feed before you commit. Ask the staff to drop a pinch of food in the tank and confirm the fish are actively striking at the surface — a clown killifish that ignores food in the store is a clown killifish you don't want to take home. If your LFS doesn't stock them, ask if they can special-order from a captive breeder; many shops will, and the fish arrive in better shape than retail-shelf imports.

For other small surface-and-mid-water nano fish that pair well in a community setup, check our guide on freshwater fish for compatibility ideas.

Signs of a Healthy Fish#

A healthy clown killifish hovers calmly at the surface, body straight, fins held erect (not clamped against the body), with sharp black banding and visible color in the tail. They should respond to food immediately, striking the surface within a second or two of food hitting the water.

Avoid any fish with a fine gold dusting on the body (velvet), white cottony patches (fungal infection), clamped fins, hollowed-out belly, or labored breathing. A fish flashing against decor or hanging limp at the surface is a stressed or sick fish. Pass on the whole tank if even one fish in it shows obvious disease symptoms — velvet in particular is highly contagious and may already be incubating in apparently healthy tank mates.

Quick Reference#

• Tank size: 5 gallons minimum for a small group; 10 gallons for a colony
• Temperature: 68-79°F (74-76°F sweet spot)
• pH: 5.5-7.5 (optimal 6.0-7.0)
• Hardness: 4-8 dGH; soft water preferred
• Diet: Micro-predator — baby brine shrimp, daphnia, microworms, crushed micro-pellets
• Tankmates: Ember tetras, chili rasboras, pygmy corydoras, neocaridina shrimp, small Boraras
• Avoid: Bettas, guppies, fast/nippy barbs, anything over 2 inches
• Lid: Tight-fitting with every gap covered — non-negotiable
• Lifespan: 3-5 years
• Difficulty: Beginner with stable parameters and a sealed lid

Related species and setups: pair this guide with the golden wonder killifish profile if you want a larger, hardier killifish, or the American flagfish for a North American killifish with strong algae-eating habits. For a turnkey nano build, the Fluval Flex is the off-the-shelf tank most clown killifish keepers eventually land on.