2 × Clown Killifish (Pseudoepiplatys annulatus)

Choose this small, surface-oriented killifish

The Clown Killifish (Pseudoepiplatys annulatus) is a small, peaceful freshwater killifish with surface-oriented behaviour that reaches up to 4 cm. It suits a keeper who can provide calm companions, a secure cover, abundant shelter and consistently clean water. This is not a fish to place casually into a busy aquarium: its size, peaceful temperament and preference for company all need to be considered before it joins an established community.

OATA’s killifish guidance describes killifish as generally small and peaceful fish that do not appreciate boisterous tank mates. It also recommends soft to medium water, a planted aquarium and an essential cover. Those requirements make this fish a better match for a deliberately planned aquarium than for an energetic mixed display.

Decide from the aquarium outward

Begin with the aquarium rather than the fish’s small appearance. A larger volume is easier to keep stable, while a mature biological filter is essential for processing waste. Check the water, cover, planting and existing livestock together; passing only one of those checks is not enough.

• Choose it when: the aquarium is filtered, mature, covered and planted, with calm livestock and water at 22–26°C, pH 5.5–7.0 and 2–8°dGH.
• Pause when: the aquarium contains fast, boisterous, aggressive, predatory, long-finned or fin-nipping fish.
• Plan socially: OATA suggests keeping at least three killifish together, so this pack of two should be considered within a wider stocking plan.
• Protect water quality: ammonia and nitrite should remain at zero, supported by regular testing and weekly maintenance.

Understand the pack and gallery before ordering

One purchase supplies a pack of two live Clown Killifish. The pack quantity describes how many fish are supplied; it does not mean that two fish form the complete social group recommended in OATA’s guidance. Plan for at least three killifish in total, then add livestock gradually so the biological filter can adjust to the extra waste and feeding.

Sex is guaranteed only when the selected option explicitly states male or female. This 2 × Clown Killifish listing has no sex-guaranteed option. OATA suggests two females to each male when planning a killifish group, but this pack should not be assumed to contain that ratio. Apply the ratio only when the sex of each fish has been assessed separately.

The gallery shows two fish for a useful visual impression, but imagery and offer quantity serve different purposes. The gallery images are representative of this type of animal rather than photographs of the exact animal supplied, so colours can look slightly different from the live animal.

What the pack changes

• Social planning: two fish are a starting quantity, while OATA suggests at least three.
• Filter loading: assess the waste from the whole planned group, not only the first two fish.
• Compatibility: screen every existing tank mate before increasing the group.
• Sex ratio: do not plan around an assumed male or female combination.

The purchase decision should therefore cover both the two fish in this pack and the aquarium’s capacity for an appropriate longer-term group. If another killifish is to be added, do so slowly and only after testing confirms that ammonia and nitrite remain at zero.

Check the decisive keeping numbers

Keep the aquarium at 22–26°C, pH 5.5–7.0 and 2–8°dGH. These are general keeping ranges for this animal. Stability matters alongside the readings: test regularly, correct the cause of any deterioration and avoid abrupt changes during routine maintenance.

For housing, OATA recommends at least 40 litres for a small group of the smallest killifish and at least 90 litres for a group of larger species over 7 cm. Use the 40-litre group figure conservatively for this fish, which reaches up to 4 cm, and favour additional water volume because larger aquariums maintain temperature and water quality more steadily.

Ammonia and nitrite should be zero mg per litre. Keep nitrate no more than 20 mg per litre above the normal level in the tap water used for the aquarium. These chemical limits, the group plan and the aquarium volume should all pass before the fish are introduced.

Build a covered, planted aquarium with shelter

Use a filtered, securely covered aquarium with gravel or sand and plenty of shelter. OATA recommends heavy planting with live plants, particularly where multiple males may be present. If live plants are not used, plastic plants and suitable ornaments such as plant pots or model caves can provide alternative cover.

A cover is essential because killifish can jump. Check the entire top of the aquarium rather than relying on a lid that leaves open spaces around equipment. The aim is a properly covered aquarium that still allows the filter and other equipment to operate as intended.

Arrange the aquarium in three layers

• At the surface: leave accessible swimming and feeding space while providing nearby plant cover for a surface-oriented fish.
• Through the middle: use planting and ornaments to provide shelter and give fish places to withdraw from activity.
• At the base: choose aquarium gravel or sand and keep it accessible enough for waste to be removed during water changes.

Flow should maintain water quality without turning the aquarium into a turbulent environment. The Clown Killifish is a calm, surface-oriented fish, while OATA warns that killifish do not appreciate boisterous companions. Observe where the fish hold position: normal use of the surface and cover is more reassuring than persistent hiding or struggling in one part of the aquarium.

Do not use planting as a substitute for water volume or filtration. Plants and ornaments provide cover, but the filter deals with waste and the water volume buffers changes. A small group of the smallest killifish still needs at least 40 litres under OATA’s planning guidance.

Final setup check

1. Confirm that the aquarium is fully covered.
2. Check that the filter is established and unobstructed.
3. Provide plants or equivalent shelter.
4. Confirm that the planned group and all tank mates fit the available volume.
5. Test ammonia, nitrite, nitrate, temperature, pH and hardness before introduction.

Mature and protect the biological filter

Use a well-established biological filter before introducing the fish. The RSPCA’s aquarium welfare guidance explains that fish release toxic ammonia, which a working biological filter converts first to nitrite and then to the safer nitrate. Ammonia and nitrite are both dangerous, so a filter is not an optional extra.

Prepare and mature the aquarium before livestock arrives. Our first tropical aquarium guide explains the preparation sequence, while the fish should be introduced only after testing shows ammonia and nitrite at zero.

Protect the bacteria that protect the fish

Check the filter for blockages as part of weekly maintenance. When cleaning is necessary, rinse the media lightly in aquarium water removed during a partial water change. Do not run the filter media under the tap. Chlorine or chloramine may kill the beneficial bacterial population established in the media.

Treat replacement tap water with a suitable conditioner before it enters the aquarium. This removes harmful chlorine or chloramine and protects both fish and filter bacteria. Match routine replacement water closely enough to avoid abrupt temperature or chemistry changes.

Add livestock slowly

Every extra fish and every increase in feeding creates more waste. Beneficial bacteria need time to increase in response. Adding too many fish too quickly can cause new tank syndrome, in which the filter cannot process the increased waste and ammonia or nitrite rises.

• Before an addition: test ammonia and nitrite and confirm both are zero.
• After an addition: continue regular testing and watch for any change in fish behaviour or feeding.
• If either rises: stop further stocking, test the full set of water values and address the water-quality problem.
• If the filter blocks: restore flow without destroying the bacterial population.

This pack contains two fish, but the biological load must be considered alongside every fish already present and any further killifish included in the social plan.

Keep water stable with weekly maintenance

Maintain 22–26°C, pH 5.5–7.0 and 2–8°dGH. Use the water chemistry guide to understand each measurement, then compare your readings with the planned range using the water matcher.

Test ammonia and nitrite at least once per week and keep both at zero mg per litre. Nitrate should not exceed 20 mg per litre above the normal level in the tap water used for the aquarium. Record readings consistently so a gradual change is seen before it becomes a larger welfare problem.

Use a repeatable weekly routine

1. Test temperature, ammonia and nitrite before maintenance.
2. Check pH, hardness and nitrate against the planned values.
3. Carry out a partial water change of 25% at least once every week.
4. Use a siphon to remove accumulated solid waste from the substrate.
5. Treat replacement tap water with conditioner before adding it.
6. Check the filter for blockages and clean it only when necessary.
7. Rinse filter media lightly in removed aquarium water, never under the tap.
8. Retest whenever fish behaviour, breathing, colour or feeding changes.

Increase investigation rather than making random chemistry changes if a reading moves outside the plan. Look for overfeeding, a blocked filter, excess waste or stocking that has increased faster than the filter can accommodate.

Respond to a poor reading

Feed small portions once a day

Use small live and frozen foods such as daphnia, brine shrimp or tubifex as the staple diet, with suitable flake as a supplement. OATA recommends feeding killifish only the amount they can eat within a few minutes, once a day.

Match each piece of food to the fish’s tiny size and surface-oriented feeding behaviour. Distribute a measured, modest amount where the fish can reach it, then watch the whole group rather than assuming that food added to the aquarium has been eaten evenly.

Use the few-minutes rule

1. Add a small initial portion.
2. Watch whether both fish locate and take the food.
3. Add no more than the group can finish within a few minutes.
4. Remove or account for uneaten food rather than leaving it to decay.
5. Reduce the next portion if food repeatedly remains.

Overfeeding harms water quality as uneaten food breaks down and releases waste. This is especially important while the biological filter is adjusting to new livestock. The correct portion is therefore defined by what the fish finish promptly, not by a fixed number of food items.

Vary food without changing the schedule

Keep the once-daily feeding schedule while rotating small live or frozen daphnia, brine shrimp and tubifex. Suitable flake can supplement this staple diet. Every item still counts towards the few-minutes portion, so variety should not increase the total amount offered.

Do not respond to poor appetite by repeatedly adding more food. A reduced intake is one of OATA’s warning signs, so combine feeding observation with water testing and a broader health check.

Plan growth around an adult size of up to 4 cm

Plan space around an adult size of up to 4 cm rather than treating the purchase quantity or initial appearance as the fish’s final requirement. The aquarium and stocking plan should continue to provide swimming room, shelter and stable water as the fish develop.

OATA recommends an aquarium of at least 40 litres for a small group of the smallest killifish. The larger the aquarium, the more stable temperature and water quality tend to be, which gives the keeper more room to manage normal changes in waste and feeding.

Recheck the plan as the fish develop

• Swimming space: confirm the group can use the aquarium without being crowded by plants, ornaments or tank mates.
• Shelter: retain enough cover for fish to withdraw from one another and from community activity.
• Filter capacity: test ammonia and nitrite after growth or stocking increases the biological load.
• Food access: watch each fish during the once-daily feeding period.
• Community balance: reassess any tank mate that becomes boisterous, aggressive or capable of treating smaller fish as prey.

Do not use colour or fin shape to promise the sex of these fish. OATA notes that male killifish are generally more colourful and have more developed finnage than females, but the offer carries no sex guarantee. Group planning should therefore be adjusted only after the fish can be assessed individually.

A larger aquarium is not a reason to stock quickly. Add fish slowly so the biological filter can adapt, and verify zero ammonia and nitrite before each planned increase. Space, filtration and group composition should progress together.

Follow the arrival sequence in order

Arrange for someone to receive the parcel because live fish must not be left unattended. Follow the steps below in order and complete the inspection on the day the parcel arrives.

1. Start filming before opening: make a continuous unboxing video for every delivery while the parcel is still sealed and the outer box is visible.
2. Open in one continuous take: keep filming until the fish can be seen inside the sealed bag, before anything is disturbed.
3. Inspect before release: check the fish while they remain in the sealed bag.
4. Float the bag: acclimatise slowly and float the bag for 20–30 minutes before releasing the fish.
5. Release the fish: move them into the prepared aquarium without pouring the bag water into the tank.

The aquarium should already be mature, filtered, covered and within the planned water range before the parcel is opened. Test ammonia and nitrite in advance rather than trying to prepare the aquarium after the fish arrive.

Keep claim evidence complete

For a Live Arrival Guarantee claim, the video must show the sealed parcel, the continuous opening and the fish still inside the sealed bag. Keep the order number with the video and contact Tropical Fish Co on the same day if anything has gone wrong. The current requirements are set out in the delivery and Live Arrival Guarantee policy.

Once released, give the fish access to the planted cover prepared for them and observe swimming, breathing and balance. Keep the cover secure, leave the filter running and protect the planned temperature and water chemistry.

Use first-week and first-month checkpoints

Use the first week to confirm that both fish are feeding, swimming appropriately and using the aquarium without persistent stress signs. The first month should establish a repeatable pattern of feeding, testing, water changes and observation rather than a series of reactive changes.

On the first day

• Complete the arrival and acclimatisation sequence in order.
• Confirm that the cover is secure and the filter is working.
• Observe swimming, breathing and balance after release.
• Keep the aquarium within 22–26°C, pH 5.5–7.0 and 2–8°dGH.

During the first week

• Feed once a day, offering only what the fish finish within a few minutes.
• Watch both fish eat rather than judging appetite from disappearing food alone.
• Check for hanging at the surface, sitting on the bottom or erratic swimming.
• Look for darker or paler colour, increased hiding or a change in aggression.
• Check for faster or slower gill-cover movement, damaged fins, missing scales, white spots, fluffy growths, bumps or ulcerations.
• Test water promptly if behaviour, breathing, appearance or feeding changes.

By the end of the first month

• Maintain a consistent partial water-change routine.
• Test ammonia and nitrite at least weekly and keep both at zero.
• Confirm that nitrate remains within OATA’s limit.
• Review the group plan because this pack contains two while OATA suggests at least three killifish.
• Check that every proposed tank mate still passes the temperament, size, water and fin-type screening rules.

If either fish shows a meaningful health change, test the water first and seek prompt guidance from Tropical Fish Co. Do not begin a disease treatment from appearance alone; water quality, behaviour, breathing, condition and feeding should be considered together before the next action is chosen.

Screen every community tank mate

Choose only calm community fish that match the aquarium’s water and space plan. OATA describes killifish as generally peaceful and says they do not appreciate boisterous tank mates. Some killifish can live in community aquariums, while others do best in a dedicated aquarium because they may be shy and prone to bullying.

Avoid boisterous fish and long-finned fish. OATA says some male killifish may be aggressive towards long-finned species. Avoid large, aggressive, predatory and fin-nipping fish. A peaceful, small fish should not be placed where it will be chased, bitten, crowded or treated as prey.

Apply four checks to every candidate

Do not treat a peaceful label as a complete compatibility decision. A fish can be peaceful yet too active, too large, long-finned or unsuitable for the same water. Equally, adequate water chemistry does not make a boisterous tank mate acceptable.

Shrimp require caution because small young shrimp may be eaten. Screen invertebrates for size, water needs and predation risk rather than assuming that a small fish is harmless to every small animal.

Where the result remains uncertain after these checks, use a dedicated killifish aquarium instead of experimenting with the animals. Compatibility should be decided before introduction, not after chasing or injury has begun.

Build the social group without rushing the filter

Plan for at least three killifish in total. OATA suggests this minimum and gives a planning ratio of two females to each male to reduce stress on females or other aquarium inhabitants. More can be kept when that ratio, aquarium space, shelter and filter capacity are all considered.

This pack contains two fish and carries no sex guarantee, so it should not be treated as proof of a complete group or of the suggested ratio. Establish the sex of individual fish separately before using sex as part of the group plan.

Use a staged stocking decision

1. Check the aquarium: confirm at least 40 litres for a small group of the smallest killifish, with a larger aquarium where the fish or community requires it.
2. Check the water: ammonia and nitrite must be zero, with temperature, pH and hardness inside the planned ranges.
3. Check the existing fish: exclude boisterous, long-finned, aggressive, predatory and fin-nipping tank mates.
4. Add slowly: allow the biological filter to adjust to each increase in waste and feeding.
5. Observe the whole group: look for persistent hiding, chasing, altered colour, damaged fins, abnormal swimming or reduced feeding.

Cover becomes particularly important when more than one male is present. OATA recommends a heavily planted aquarium to provide shelter, especially for multiple males. Increase usable shelter as well as headcount; an extra fish without extra cover can change the social pressure in the aquarium.

If the filter cannot maintain zero ammonia and nitrite after an addition, stop increasing the group and correct the water-quality problem. Social planning cannot be separated from biological capacity: a larger group is appropriate only when the aquarium can support it safely.

Get clear answers to common Clown Killifish questions

How big does Pseudoepiplatys annulatus get?

The Clown Killifish reaches up to 4 cm. Plan the aquarium around that adult size rather than the fish’s size when supplied.

What aquarium size do 2 × Clown Killifish need?

OATA recommends at least 40 litres for a small group of the smallest killifish. Use a filtered, covered aquarium and favour more water volume for greater stability.

How many Pseudoepiplatys annulatus should be kept together?

OATA suggests keeping at least three killifish together, with two females to each male as the planning ratio. Add fish slowly and apply that ratio only after individual sex has been assessed.

Is this fish suitable for a beginner?

It needs moderate care, including a mature, filtered and covered aquarium, regular water testing, consistent maintenance and protection from boisterous tank mates.

What should I feed Pseudoepiplatys annulatus?

Use small live and frozen foods such as daphnia, brine shrimp or tubifex as staples, with suitable flake as a supplement. OATA recommends only what the fish finish within a few minutes, once a day.

What temperature and pH does Pseudoepiplatys annulatus need?

Keep it at 22–26°C and pH 5.5–7.0, with 2–8°dGH. Keep ammonia and nitrite at zero mg per litre.

Is the Clown Killifish aggressive or likely to nip fins?

It is peaceful, but OATA says some male killifish may be aggressive towards long-finned fish. Avoid long-finned, boisterous, aggressive and fin-nipping tank mates.

Which animals can this fish live with?

Consider only calm community fish that match its water, space and size requirements. Avoid boisterous, long-finned, aggressive, predatory and fin-nipping fish; use a dedicated aquarium when a combination remains uncertain.

How does Pseudoepiplatys annulatus arrive alive in the UK?

Tropical Fish Co’s policy says fish are hand-bagged in oxygen and packed in an insulated box, with a heat pack when the weather calls for it. Be present to receive the parcel, film it continuously from sealed, inspect the fish in the sealed bag and float the bag for 20–30 minutes before release.

Read the public references

• OATA, “How to look after killifish”: group husbandry, water values, housing, feeding, maintenance, social planning and compatibility.
• RSPCA aquarium environment guidance: biological filtration and the processing of ammonia, nitrite and nitrate.
• Tropical Fish Co delivery and Live Arrival Guarantee policy: packing, receipt, continuous unboxing video, inspection and acclimatisation steps.