Knowledge Centre · Species guidance

Clown killifish care: when "small tank fish" is actually true

Epiplatys annulatus is one of the few community fish where "suitable for a small tank" is genuinely true rather than a marketing simplification. Adults stay around 3–3.5cm, spend almost all their time hovering just beneath the surface, and need very little swimming room by fish standards. What they do need, specifically, is a tight-fitting lid, gentle rather than strong flow, food small enough for their tiny mouths, and tankmates that won't out-hustle them for either. None of that makes "small tank" mean low-maintenance: stability and upkeep still matter just as much as in a larger aquarium.

Before adding clown killifish

May be suitable when…

You can keep a small group in a properly cycled tank of at least around 20 litres, your lid is properly tight-fitting, your filtration produces gentle rather than strong surface flow, and you're prepared to feed very small foods rather than standard community flake.

Reconsider when…

You're planning to keep just one or two, your tank isn't properly cycled and maintained despite being small, your filter produces strong surface turbulence, or your other stock is likely to outcompete a very small, gentle surface feeder for food.

Worth knowing: a small aquarium doesn't mean a low-maintenance one — a small volume of water is less forgiving of ammonia and nitrite spikes than a large one, not more.

Identification and size

Epiplatys annulatus (Boulenger, 1915), also called the clown killifish or banded panchax, is a small West African killifish, typically reaching only around 3–3.5cm (roughly 1.3in) as an adult[1]. Its pale, torpedo-shaped body carries several bold dark bands, and mature males develop a distinctive lyre-shaped tail with red, blue and yellow colouration used in display toward females and rival males[2].

This is an unusually tiny fish, and that's central to almost everything else in this guide. Its tank-size tolerance, food-size requirements and tankmate compatibility all follow directly from how small it actually is, not just how it's marketed.

Water conditions that matter most

Treat the ranges below as a practical starting point drawn from specialist care sources, not a single precise scientific target.

Gathered from specialist killifish-keeping sources; treat as a practical range rather than one confirmed figure.
Factor	Commonly reported range	Notes
Tank size	From around 20L (5 US gal) minimum for a small group; 40–60L (10–15 gal) preferred	Genuinely realistic for a small aquarium, unlike many fish marketed that way — but still needs to be properly cycled and maintained.
Temperature	Roughly 22–26°C (72–79°F)	Moderate tropical range; avoid the warmer extremes some tropical setups run at.
pH	Roughly 5.5–7.5	Soft, slightly acidic water is often described as preferred, reflecting its native West African habitat.
Ammonia / nitrite	Zero	A small water volume is less forgiving of a spike, not more — see our ammonia and nitrite guides.

Surface behaviour, flow and cover

This species is an almost exclusively surface-dwelling fish, reported to spend the great majority of its time hovering just beneath the water's surface, largely motionless, waiting to strike at small insects and other tiny prey[2]. Strong surface agitation or turbulent flow works against that natural behaviour, so gentle filtration — enough to keep the water clean without churning the surface — suits this species better than a powerful filter outlet aimed across the top of the tank.

Floating plants and dense surface or near-surface cover (Amazon frogbit, duckweed in moderation, or similar) are commonly recommended, both to diffuse light and to give this naturally cautious fish somewhere to retreat to and feel secure while still staying in its preferred zone near the top of the water column.

Why a secure lid matters

Treat a tight-fitting lid as essential, not optional. This species' constant proximity to the surface combined with a genuine capacity for jumping makes any gap around the tank's edge, filter pipes or cables a real escape route, and specialist sources are consistent on this point[2]. Given how small and slim-bodied this fish is, even a gap that looks insignificant is worth checking and sealing before adding it to a tank.

Keep clown killifish in a proper small group rather than a single pair, ideally around six to ten individuals, with more females than males commonly recommended — roughly one male to every two or three females is a frequently cited ratio[2]. A larger group is reported to help individuals feel more settled and display more natural social and courtship behaviour than a minimal pair or trio.

Feeding: why food size matters more than food type

As a strictly surface-feeding micro-carnivore, this species needs food that's actually small enough for its mouth, not just generically "small fish food." Specialist sources specify floating foods under roughly 0.3mm (crushed flake or purpose-made micro-pellets) alongside small live foods such as baby brine shrimp or micro worms[2]. Standard community flake, sized for typical tetras or livebearers, is often too large for this fish to take effectively, which is an easy detail to miss if you're stocking a mixed community tank and feeding everything the same food.

Tank mates and compatibility

The main compatibility risk with this species runs in a specific direction: it's the one likely to be outcompeted, not the one causing problems. Fast, assertive surface or mid-water feeders can out-hustle this small, relatively passive fish for food, and any tankmate large enough to view it as prey is an obvious risk given its size[2]. Calm, similarly small bottom-dwelling or lower-water-column tankmates — and dwarf shrimp, which largely occupy a different zone of the tank — tend to work better than boisterous surface competitors.

See our guide to choosing tank mates for a broader framework on working through a stocking decision like this one, keeping in mind that "small and peaceful" tankmates still need to be gentle feeders specifically, not just non-aggressive in temperament.

Normal behaviour

Hovering nearly motionless just beneath the surface — the core, expected behaviour for this species, not lethargy.
Sudden short strikes at food or tiny prey — normal predatory feeding behaviour for a micro-carnivore.
Males displaying flared, colourful fins toward females or rival males — normal courtship/territorial display, not injury.
Sheltering within floating plant cover — a normal use of the habitat this species is provided, not constant hiding out of distress.

Warning signs and what to check first

None of the signs below confirms a specific problem on its own. Each has more than one possible explanation, and reacting immediately — especially with a large water change or a new product — before checking the more likely causes can make things worse.

Visible thinning or reduced condition despite feeding

What it might mean: Food that's too large for it to actually eat, or being consistently outcompeted by faster tankmates.

What else could explain it: Normal size variation between individuals in a group.

Check this first: Whether the food you're offering is fine enough for its mouth, and whether this individual is actually observed successfully feeding.

Don't: Assume "the tank gets fed" means every individual is getting enough of the right size food.

A fish missing from a small, low-decor tank

What it might mean: It has jumped through a lid gap — a real risk for this species given its size and surface-dwelling habit.

What else could explain it: It's tucked deep into floating plant cover you haven't checked thoroughly.

Check this first: The floor and area around the tank, then every lid gap, then floating plant cover.

Don't: Leave a lid gap unaddressed after finding one missing fish.

Sudden ammonia or nitrite reading in a small tank

What it might mean: A cycle disruption, overfeeding, or overstocking — and it will typically show up faster and more severely than in a larger volume.

What else could explain it: A recent water-testing error rather than a genuine spike.

Check this first: Retest to confirm, then check feeding amounts and total stock against tank size.

Don't: Assume a small, simple-looking tank is inherently lower-maintenance — the opposite is generally true for water stability.

Common mistakes

Feeding standard-sized community flake, which is often too large for this species to eat effectively.
Leaving lid gaps unaddressed, underestimating a small, surface-dwelling fish's jumping ability.
Running strong surface flow, working against this species' natural, calm-surface hovering behaviour.
Keeping too few, rather than a proper small group with more females than males.
Treating "small tank" as "low maintenance", when a small volume is actually less forgiving of water-quality swings.
Combining with fast, assertive feeders that outcompete this gentle surface feeder for food.

Watching water quality in a small tank

Small tanks can suit this species, but they also swing on water chemistry faster than large ones, which makes regular checking more useful, not less. Logging readings with Water Check gives you a plain-language read on ammonia, nitrite, pH and temperature trends over time, so you can catch a small-volume swing before it becomes a problem for a fish this size.

Frequently asked questions

How small a tank can clown killifish actually live in?

Specialist sources generally suggest a working minimum of around 20 litres (5 US gallons) for a small group, with something closer to 40-60 litres (10-15 gallons) preferred for a comfortable group of six to ten. It's one of the more realistic small-tank community fish in the hobby, but "small tank possible" still means a properly cycled, stable, well-maintained one — not that ordinary aquarium care can be skipped because the volume is low.

Do clown killifish need a lid?

Yes, and it should fit tightly. This species spends most of its time near the surface and is a capable jumper, so any gap around the tank's edge, filter pipes or cables is a realistic escape route for a fish this small and slim-bodied.

What do clown killifish actually eat?

Very small food is essential, not a nice-to-have. As surface-feeding micro-carnivores, they need floating foods small enough to fit their tiny mouths — crushed flakes or purpose-made micro-pellets under roughly 0.3mm are commonly recommended, alongside small live foods like baby brine shrimp or micro worms. Standard-sized flake or pellet food intended for typical community fish is often too large for them to eat effectively.

Can clown killifish live with shrimp?

Generally yes, since adult clown killifish are too small to threaten adult dwarf shrimp and largely occupy different zones of the tank — the killifish at the surface, shrimp lower down. The main caution runs the other way: very young killifish fry are small enough that some shrimp could view them as food, which is worth bearing in mind if you're specifically trying to breed this species in a shrimp tank.

Sources and uncertainty

Published: 30 July 2026
Last reviewed: 6 August 2026
Written and maintained by: AquaPulse (Valeon Labs Ltd)

This guide draws on the Integrated Taxonomic Information System (ITIS) for species identification, and specialist killifish- and aquarium-keeping sources for day-to-day husbandry, since dedicated captive-welfare research specific to this species is limited. We've been explicit about which figures reflect specialist/hobbyist consensus rather than a formal study. We'll update this page if we find something we've got wrong.

Good to know: This guide provides general informational guidance only. It is not a substitute for specialist aquatic-veterinary advice.

[1] Integrated Taxonomic Information System (ITIS) — "Epiplatys annulatus (Boulenger, 1915)" (TSN 646908) Used as the taxonomic authority for species name and author citation.
[2] Aquarium Co-Op — "Care Guide for Clown Killifish" Specialist retailer/hobbyist source. Used for adult size, surface-dwelling behaviour, lid/jumping risk, group structure and sex ratio, feeding/food-size requirements, and tankmate/shrimp compatibility. Not a scientific authority.

Facts we couldn't pin down: a precise lifespan figure, since hobbyist estimates ranged from roughly two to five years and we found no single dedicated longevity study to confirm one; and specific breeding/rearing instructions, since we judged this outside the scope of a general keeping guide.