Clown Killifish: A Complete Nano Aquarium Care and Breeding Guide

Reaching barely an inch long, this tiny annual fish thrives in nano setups from five gallons upward.4-inch West African surface dweller with neon red, gold, and electric-blue bands, scientifically known as Epiplatys annulatus. It thrives in soft, tannin-stained, slightly acidic water at 73 to 79°F, eats small live and frozen foods sized to a 3 to 4 cm mouth, and breeds readily in a 5 to 10-gallon nano tank with floating plants and a tight lid.

Below, you’ll find what to look for when buying, the exact water chemistry that matches their swamp biotope, a realistic food-sourcing plan, sexing tips, and a step-by-step breeding protocol that takes fry to adulthood.

Meet the Clown Killifish, One of the Smallest Killifish in the Hobby

Bright bands of red, gold, and electric blue run along a slender 1.2 to 1.5-inch body, and a forked tail fans out like a pennant. The fish hovers just under the surface, watching the room. That combination of size, color, and surface-stalking behavior is the reason aquarists call this fish the clown killifish and also the rocket killifish.

Scientific Identity and the Naming Question

The valid scientific name is Epiplatys annulatus, but you’ll see Pseudepiplatys annulatus on older stock labels, in European breeder catalogs, and across import paperwork. Both refer to the same species, and the reclassification is the reason so many buyers end up searching one name and finding information under the other. When shopping online or talking to a breeder, either name is fine; what matters is the banded pattern, the body shape, and the source stock.

Native Range and Natural Habitat

Populations of Epiplatys annulatus span Guinea, Sierra Leone, and Liberia, where they live in slow, shaded forest streams and the edges of swamp pools. The water is tannin-stained, soft, and slightly acidic, often shaded by overhanging roots and thick mats of floating plants. Replicating that environment is the single biggest reason groups settle in and color up.

Size, Shape, and the “Rocket” Nickname

Adults top out at roughly 1.2 to 1.5 inches (3 to 4 cm), with an elongated, slightly compressed body and a broad, symmetrical tail. The stretched silhouette and the way the fish seems to be launched forward at the surface explain the rocket killifish nickname. Males grow a touch larger and flash longer fin extensions as they mature.

Lifespan in the Wild and in Your Tank

Like many killifish, this species has an annual life cycle in the wild, surviving dry seasons as eggs and living only a few months as adults. In a stable aquarium, individuals commonly reach 2 to 3 years, with well-kept groups occasionally pushing past 3. Long life in the hobby is the direct result of steady water, varied food, and a calm group dynamic.

Surface-Dwelling Behavior

These fish almost never venture to the bottom. They patrol the top inch of the water column, snap food from the surface, and rest just below the meniscus. That behavior drives every equipment decision that follows, from tank height to lid fit to filter flow direction.

That surface-driven behavior also shapes how a proper tank should look, down to the waterline and the tannins above it.

Trait	Detail
Scientific name	Epiplatys annulatus (syn. Pseudepiplatys annulatus)
Adult size	1.2 to 1.5 inches (3 to 4 cm)
Native range	Guinea, Sierra Leone, Liberia
Habitat	Slow streams, swamp pools, tannin-stained water
Lifespan in aquaria	2 to 3+ years
Behavior	Surface-dwelling, peaceful, micro-predator

Recreate the West African Swamp Habitat in a Nano Tank

The tank is small, but the water inside it needs to match the swamp. Stable, soft, slightly acidic water with low flow and dense cover is the environment your fish evolved to recognize, and it’s the environment where they display their best color.

Tank Footprint, Volume, and Why Long Beats Tall

A 5 to 10-gallon tank with a long, shallow footprint works well for a group of six to eight fish. The surface area matters more than the depth, because these fish live at the top. A standard 10-gallon long (20 x 10 x 12 inches) gives more swimming room and surface area than a tall 10-gallon cube of the same volume, and the lower water column keeps food and fish visible.

Water Chemistry Pulled From the Biotope

Aim for pH 6.0 to 7.0, general hardness under about 8 dGH, carbonate hardness under 4 dKH, and a steady 73 to 79°F. Tannin-stained water from Indian almond leaves, alder cones, or peat pulls the chemistry closer to the swamp and softens light. Wild populations span a range of swamp conditions, but in captivity, fish consistently do best in soft, slightly acidic water rather than the hard, alkaline tap many US hobbyists use straight from the faucet.

Substrate, Leaf Litter, and Floating Cover

Dark sand or fine gravel sets a natural stage, and a layer of catappa leaves deepens the tannin tint while feeding beneficial microfauna. Floating plants, including frogbit, red root floaters, and water sprite, break the surface glare and give fish the shaded lanes they use to patrol. A dim LED fixture or floating plants alone often produces stronger color than bright overhead light.

Filtration That Keeps the Surface Calm

A small sponge filter driven by a low-flow air pump, or a hang-on-back filter with the outflow turned against the glass, keeps current gentle at the top. These fish dislike a strong surface ripple, and any flow that pushes them around the tank also suppresses display and feeding.

Why a Tight Lid Is Non-Negotiable

“A snug, gap-free lid isn’t optional. Clown killifish jump, especially during feeding frenzies and when startled, and an uncovered nano tank is an open exit.

Sliding glass lids with sealed corners or a fitted mesh cover that sits flush with the rim keeps the group safe. Leave at least an inch of airspace between the waterline and the lid so fish can use that surface layer comfortably.

Feed a Diet Built Around Tiny Live and Frozen Foods

Standard dry flakes alone will not sustain a nano predator that hunts mosquito larvae and daphnia in the wild. Closing the nutritional gap is what turns a surviving group into a thriving, breeding-ready one.

Core Foods Sized to a 3 to 4 cm Mouth

Match food size to the fish. Items larger than the mouth will be ignored, and items too small rarely satisfy hunting instincts. A core rotation that works across the year includes:

• ▸Baby brine shrimp: Newly hatched nauplii trigger an instant feeding response and provide fats and protein ideal for conditioning breeders.
• ▸Daphnia: Live or frozen daphnia offers gentle roughage and helps prevent the constipation dry-only diets can cause in tiny fish.
• ▸Microworms: Cultured at home in a small jar, microworms stay suspended near the surface and are perfect for new juveniles and shy adults.
• ▸Chopped blackworms: Chopped live blackworms are protein-rich and easy to portion into mouth-sized pieces for adult fish.
• ▸Grindal worms: A mid-size step between microworms and blackworms, useful for growing juveniles and conditioning pairs.

Where to Get the Food

Local fish stores often carry live blackworms and frozen baby brine, though selection varies by region. Mail-order cultures from aquarium hobby suppliers ship microworm, grindal worm, and daphnia starter cultures year-round. Culturing microworms and BBS at home requires a few mason jars, yeast or a piece of bread for microworms, and a small hatchery for brine shrimp eggs, both of which pay for themselves within weeks.

Feeding Frequency and Hunting Rhythm

Small, frequent meals match their metabolism and surface-stalking style. Two to three feedings per day of small portions beat one large feeding. Offer only as much as the group clears in two to three minutes; leftover food clouds the water and feeds hair algae in a low-flow setup.

Transitioning New Fish and Recognizing Non-Eaters

“Newly imported clown killifish often refuse dried food at first. Offer live baby brine or microworms for the first week, then mix in frozen and dry options as the group settles.

A fish that hangs at the back of the tank, ignores passing food, and shows clamped fins is failing to transition. Watch the group for several minutes after each feeding to confirm every individual is eating; shy fish can fall behind fast in a group setting.

Sexing Males and Females, Schooling Behavior, and Tank Mate Choices

Once a group settles, the differences between male and female clown killifish become impossible to miss. Recognizing those differences shapes every choice about ratios, group size, and the company they keep.

Male vs Female at a Glance

Feature	Male	Female
Body color	Bright red and electric-blue vertical bands	Tan to light brown, faint banding
Fins	Extended dorsal, anal, and tail filaments	Shorter, rounded fins
Size	Slightly larger, slimmer	Smaller, plumper-bodied
Behavior	Displays, fin flares, mild sparring	Calmer, often paler when stressed

Juveniles look nearly identical until they reach about 1 inch, and sexing improves with age. A group of six to eight juveniles usually reveals a clean male-to-female ratio within six to eight weeks.

Group Size and Why Six to Eight Matters

Keeping at least six to eight of them together diffuses male sparring and coaxes out vivid fin displays. With only two or three males in a small tank, dominant individuals harass subordinates until they hide and stop eating. More fish in the group means no single target takes the brunt of the chasing, and females display better when multiple males are competing for attention.

Compatible Tank Mates

Pick companions that swim a different zone, top out near an inch, and match a calm, non-nippy temperament. Good options include chili rasboras, ember tetras, dwarf corydoras, and otocinclus. The added movement in the midwater and bottom layers brings the top-dwelling clown killifish out to display rather than hide.

Shrimp Compatibility

Adult cherry shrimp usually survive alongside it, but shrimp fry will be hunted. A heavily planted tank gives fry enough cover to dodge predation, and many breeders run a separate shrimp colony in a quiet tank while letting the killifish tank host a small cleanup crew of adults.

Species to Avoid

“Skip any tank mate that can fit an adult it in its mouth, or that picks at long fins. Tiger barbs, large tetras, gouramis, and most cichlids will quickly stress or consume a 1.4-inch surface fish.

Fast midwater swimmers like danios and larger rasboras outcompete the group at feeding time and create a current these fish dislike.

Avoiding those bullies makes breeding far easier, since a calm, well-fed group naturally progresses into spawning condition.

Breeding Clown Killifish, From Conditioning Pairs to Raising Fry

it breeding rewards patience. The species lays a manageable number of eggs daily, accepts a mop or fine plant for spawning, and tolerates a small, calm breeding setup better than most killifish.

Conditioning and Setting Up a Breeding Tank

Feed adults generously on live baby brine, chopped blackworms, and daphnia for two to three weeks before pulling a pair or a small trio. A 3 to 5-gallon tank with a tight lid, a small sponge filter on low flow, and a spawning mop or a clump of java moss works well. Match the main tank’s water, especially pH and temperature, so the move does not shock the breeders.

Spawning Mops and Daily Egg Collection

A spawning mop made of dark acrylic yarn gives eggs a place to land away from adult appetites. Males display around the mop in the morning, and females deposit eggs one or two at a time over several days. Daily collection keeps predation low: lift the mop, swirl it gently in a shallow dish of tank water, pick the clear eggs with a pipette or soft tweezers, and move them to a small incubation container with a few drops of methylene blue or a single alder cone to prevent fungus.

Incubation and the Hatching Window

Eggs hatch in roughly 10 to 14 days at 76°F. A fertile egg develops a visible embryo and small dark eye spots before hatching; a fungused egg turns opaque white and should be removed to protect the rest. Maintain a gentle airstone in the incubation container and change a small portion of the water every other day.

First Foods and Day-by-Day Progression

1. 1Days 1 to 3 after free-swimming: Infusoria or a few drops of green water for the smallest fry; vinegar eels work as a parallel option for slightly larger mouths.
2. 2Days 4 to 10: Freshly hatched baby brine shrimp, offered twice daily in small amounts so fry don’t have to chase food across the tank.
3. 3Days 10 to 21: BBS plus microworms; introduce finely crushed dry food only after fry are visibly taking it.
4. 4After week 3: Move to grindal worms, small frozen daphnia, and finely chopped blackworms as the fry approach a half inch.

Growth Milestones and Common Failure Points

By two weeks, healthy fry show clear bands and feed actively. By four weeks, they should reach roughly half an inch and start showing early sex differences. By eight weeks, most are near adult size and ready to join the main group. The most common failure points are bacterial blooms from overfeeding, sudden temperature swings, and jumping losses from uncovered rearing containers. A tight lid, measured feedings, and small daily water changes cover most of those issues.

Long-Term Health, Troubleshooting, and Honest Limits of the Species

A settled group is hardy. An unsettled group is fragile, and the difference almost always traces back to water, flow, or food size. Reading your fish’s behavior in the first 30 days tells you most of what you need to know.

Signs of a Thriving Group

Active surface patrol, bright banding, fin extensions on males, regular spawning in mops or plants, and visible feeding within seconds of food hitting the water all signal a stable system. Color that fades for several days in a row usually means a water issue or a bully in the group, not illness.

Warning Signs of Stress or Disease

Clamped fins, heavy breathing at the surface, white film on the body, and hiding that lasts longer than a few minutes after a water change are the early indicators worth catching. Ich, velvet, and bacterial infections all respond better when caught in the first 48 hours.

Why Hard, Alkaline, or High-Flow Water Causes Decline

Mineral-heavy, alkaline, or fast-flowing water overwhelms the gills and kidneys of soft-water fish while burning energy they cannot recover. The fix is straightforward: cut flow at the surface with floating plants, mix in RO or distilled water to lower GH and KH, and recheck pH after each adjustment. A small, cheap TDS meter gives you the fastest read on whether your source water suits the species.

Managing the Annual-Fish Instinct

Older adults in stable conditions don’t necessarily follow the wild annual cycle, and breeding can continue year-round. That said, a slightly cooler, lower-feeding rest period of a few weeks in late winter sometimes triggers stronger spawns afterward. A dry-season simulation isn’t required, and chasing it often does more harm than good in a species that has been captive-bred for generations.

Realistic Expectations

“Once a it group is past the 30-day settling window, it’s a hardy, low-fuss species. Before that window closes, it punishes unstable parameters faster than almost any nano fish in the hobby.

Plan the first month around stability: matched water, gentle flow, a tight lid, and a steady supply of small live or frozen food. After that, the species rewards you with color, behavior, and a reliable breeding colony.

Key Takeaway

Success with it comes down to three decisions: matching the soft, slightly acidic water of their West African swamp, feeding small live or frozen foods sized to a 3 to 4 cm mouth, and keeping a tight lid on a long, low-flow tank with at least six to eight fish. Get those right, and the rest, including breeding, falls into place with surprisingly little extra effort.

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