Ansorge's Bichir (Polypterus ansorgii)

Choose Ansorge's bichir only if you can house a giant

Ansorge's bichir (Polypterus ansorgii) is a rarely seen West African bichir, also sold as the Guinean bichir. Like every bichir it is an ancient-looking, air-breathing fish: a long, almost round body covered in thick, diamond-shaped scales, a broad head with tube-like nostrils, large fan-shaped pectoral fins and a row of separate spiny finlets running down the back to a rounded tail. Ansorge's bichir is greenish-brown to almost black, with large, dark, irregular blotches along the sides.

FishBase records that the species was described in 1910 from the Corubal River in Guinea-Bissau and has since been reported from the Niger basin in Guinea and from Lake Kainji and the Ogun River in Nigeria. It counts 13 to 15 dorsal finlets and describes the body as elongated with a circular cross-section. Wikipedia notes that the lower jaw may protrude very slightly in mature fish and that the species is easily confused with other bichirs; it is named after the explorer William John Ansorge, who collected the first specimen.

Know the names and the size dispute

The sources disagree, so this page plans for the larger figure. A fish that may reach 60 to 90 cm is a lifetime commitment that needs a very large aquarium, not a community tank. AquaInfo's species article describes it as a rarity in the hobby because its natural range is small, and adds that it is often mistaken for a smaller form of Polypterus bichir, from which it differs in having blotches rather than long stripes.

Compare it with the other bichirs in our loaches and oddballs range, the full Polypterus bichirs category or the wider other freshwater fish section. Unusual species like this one also appear in our rare and collector fish selection.

Check what you receive

One purchase supplies one live Ansorge's bichir in the standard size we stock. That is a juvenile or young fish, not the adult size, and the sex is not selected or guaranteed. Bichirs are usually wild-caught imports, so each fish is an individual: the blotches differ from fish to fish, and the photographs show the species, not the exact animal you will receive.

Adult bichirs can be sexed by the anal fin, which is thicker in males according to Seriously Fish. Young fish cannot be sexed reliably, and this species is not known to have been bred in captivity, so buy it as a single show fish rather than with breeding in mind.

Plan for the adult, not the juvenile

• Space: the tank you start with is temporary. Have a plan, and a budget, for a much larger aquarium within a few years.
• Time: AquaInfo gives a lifespan of 10 to 15 years in the aquarium.
• Tank mates: anything the bichir can swallow as an adult will eventually be eaten, so choose the community around its final size.
• Rehoming: never release an aquarium fish into the wild. OATA points out that it is illegal and, for most fish, leads to a slow death.

Check our delivery and Live Arrival Guarantee policy before ordering, and have the aquarium running, matured and tested first.

Plan the aquarium around a 60 cm-plus adult

Bichirs live on the bottom, so floor space matters far more than height. Seriously Fish says exactly that for both the Senegal and the saddled bichir. AquaInfo says young Ansorge's bichirs can start in a tank from 80 cm, but that they grow quickly and soon need a very large aquarium.

For the adult, the closest published guide is Seriously Fish's profile of the saddled bichir, a lower-jawed relative that reaches 75 cm. It recommends a base of 210 x 120 cm, with a 90 cm height giving about 2,268 litres, for a fully grown fish. OATA's guidance for very large fish adds that tanks often need to be well over 500 litres, and that indoor heated ponds are a realistic alternative for the biggest species.

Use a three-stage tank plan

Our tank volume calculator turns your measurements into real litres. Measure the footprint rather than relying on the label on the box: a bichir needs to turn its whole body comfortably and to lie fully stretched out on the floor.

Build a floor-space layout with a locked lid

Seriously Fish recommends a soft substrate with driftwood and smooth rocks for hiding places; plants are optional. AquaInfo adds open swimming space, plenty of shelter, slightly dimmed lighting and some surface resting places such as floating plants or wood near the top, which young or newly arrived bichirs use. Anchor plants firmly, because bichirs forage through vegetation.

The lid matters more than anything else in the layout. Both sources call bichirs escape artists: AquaInfo says they can push up lids and light hoods. Fit a heavy, tight cover with every cable hole sealed. At the same time, leave a layer of air between the water and the lid, because bichirs must breathe at the surface. Seriously Fish warns that a bichir may drown if it cannot reach atmospheric air.

Divide the footprint by purpose

Avoid sharp rocks and rough gravel: the bichir lies on the bottom and pushes into gaps. AquaInfo also warns that the rear finlets are razor sharp, so never catch a bichir by hand; guide it into a container instead of netting it whenever you can.

Set warm, clean water and keep it stable

No source gives full water values for this species alone, so the table combines AquaInfo's species figures with Seriously Fish's values for two related bichirs. Keep the water steady inside the overlap rather than chasing a single number.

Match your tap water first

UK tap water ranges from soft to very hard depending on the region. Most supplies fall inside, or close to, the hardness range above, so a bichir rarely needs special water; what it needs is clean, dechlorinated, stable water. Test your tap supply for pH and general hardness before the fish arrives. Our water chemistry guide explains pH, GH and KH, and the water matcher compares your readings with the ranges in the table.

Filter for a big meat-eater

A large carnivore produces a lot of waste. OATA calls a filter essential for very large fish and says several large aquarium filters, or a pond filter, may be needed to cope. For the Senegal bichir, Seriously Fish suggests filtration turning the tank volume over four to five times an hour. Spread the outflow along the tank so the bichir still has calm resting places on the floor. Our guide to aquarium filtration covers sizing.

The biological filter must be mature before the fish arrives; the guide to the nitrogen cycle explains how to establish it. A tank that has only just been filled is not ready for a fish of this size, however small it is on arrival.

Follow a weekly routine

1. Test ammonia, nitrite, nitrate, pH and temperature.
2. Siphon uneaten food and waste from the sand; meaty leftovers foul water quickly.
3. Change at least 25% of the water, the minimum OATA recommends every week.
4. Treat the new water with a conditioner and match its temperature before adding it.
5. Rinse filter media only in water removed from the tank, never under the tap.

Feed meaty foods at dusk

Bichirs have poor eyesight and find food by smell, according to Seriously Fish, and are most active at dusk and at night. They are carnivores. AquaInfo lists mysis, mosquito larvae, shrimp, krill, mussel, squid, earthworms and pieces of fish meat as suitable foods, and advises against oily salmon and feeder goldfish. Seriously Fish's saddled bichir profile notes that large bichirs often refuse dried foods at first, though some learn to take pellets, and suggests prawns, earthworms, mussel and lancefish.

OATA's guidance for very large fish is to feed once a day, only as much as is eaten within a few minutes. Young, growing bichirs can have smaller meals more often; adults do well on a meal every day or two.

Build one measured meal

• Main course: frozen mussel meat or large frozen krill, fully thawed.
• Variety: live earthworms, chopped to size, are a favourite of many bichirs.
• Dry food: try a sinking food such as medium carnivore pellets; accept that some fish ignore it.
• Timing: feed near lights-out and place the food where the bichir can find it, ahead of faster tank mates.

Remove leftovers after a few minutes. A healthy bichir has a gently rounded belly; a sunken belly means it is losing out to tank mates or not finding the food.

Introduce it calmly and watch the first weeks

OATA's guidance for wild-caught fish is to keep lighting dim, to quarantine new arrivals before mixing them with existing stock, and to expect that some will want live or fresh food before prepared foods. Seriously Fish adds that most bichirs on sale are wild-caught and may carry infections or parasites, so watch new arrivals closely for the first few weeks. AquaInfo names a skin fluke often found on wild bichirs and warns that they tolerate many medicines poorly, suggesting half to two-thirds of the usual dose if treatment is needed.

Use OATA's floating-bag method

1. Switch off the aquarium lights.
2. Float the sealed bag for 10 minutes so the temperatures match.
3. Add small amounts of aquarium water to the bag over up to 20 minutes.
4. Guide the fish into the aquarium, keeping the bag water out.
5. Keep the lights off for the rest of the day and close the lid at once.

Our guide to acclimatising new fish walks through the same steps. AquaInfo notes that new and young bichirs often hang at the surface; that is normal while they settle.

Choose tank mates too big to swallow

Ansorge's bichir is not aggressive, but it is a predator. Seriously Fish says bichirs cannot be trusted with tank mates that fit in their mouths and are otherwise relatively peaceful. AquaInfo adds that slender fish up to about two-thirds of the bichir's length are at risk, that bichirs usually tolerate others of similar size, and that territorial cichlids, snakeheads and Labeo sharks make poor companions. It also warns that suckermouth catfish may rasp at a bichir's skin.

Screen each tank mate

Smaller bichirs such as the Delhezi Bichir or the Ornate Bichir can share a very large tank while sizes are similar, but plan ahead: an Ansorge's bichir may outgrow them. Our tank mates tool helps you check sizes and temperaments before you mix species.

Watch the bichir and act on changes

Bichirs are hardy fish: Seriously Fish describes the related Senegal bichir as very hardy and long-lived. Most problems come from poor water, a lid that is not secure, or tank mates that steal food or nip. Look at the fish every day, ideally at feeding time when it is active.

Pair each sign with an action

Answer Ansorge's bichir buying questions

What is Ansorge's bichir?

Ansorge's bichir (Polypterus ansorgii), also called the Guinean bichir, is a large, air-breathing bichir from West Africa. It was described in 1910 from the Corubal River in Guinea-Bissau and has since been reported from Guinea and Nigeria. It is olive to dark brown with large dark blotches and a row of small spiny finlets along its back.

How big does Ansorge's bichir grow?

Much bigger than many care sheets say. FishBase lists 28 cm, but Wikipedia gives 72 cm and a Dutch species article puts the maximum at up to 90 cm, saying the 28 cm figure is wrong. Plan for a fish of 60 cm or more.

What size aquarium does it need?

A juvenile can start in a tank of about 80 cm, but it grows quickly. For an adult, plan on the scale Seriously Fish gives for the similar-sized saddled bichir: a base of about 210 x 120 cm. OATA notes that very large fish often need well over 500 litres.

What water does it need?

Warm, clean, soft to moderately hard water. The published ranges overlap at about 24 to 27 degrees C and pH 6.5 to 7.5, with ammonia and nitrite at zero and nitrate no more than 20 mg/l above your tap water.

What does Ansorge's bichir eat?

Meaty foods: mussel, prawn, krill, mysis, earthworms and pieces of white fish, plus a sinking carnivore pellet if it learns to take one. Feed at dusk or after lights-out, because bichirs find food by smell.

Is it safe with other fish?

It is peaceful towards fish it cannot swallow, but it will eat smaller fish, especially slender ones. Choose large, calm tank mates such as big Synodontis, datnoids and large knifefish, and avoid aggressive cichlids, snakeheads and armoured suckermouth catfish.

Why does it swim up to the surface?

Bichirs breathe air as well as water. Rising to gulp air is normal behaviour, and Seriously Fish warns they can drown if they cannot reach the surface, so never cover the whole water surface.

How long does it live?

A Dutch species article gives 10 to 15 years in the aquarium, and other bichirs have lived much longer, so treat it as a long-term commitment.

Consult the care references

• FishBase: Polypterus ansorgii, Guinean bichir: valid name and author, common name Guinean bichir, type locality (Corubal River, Guinea-Bissau), later records from the Niger basin in Guinea, Lake Kainji and the Ogun River in Nigeria, fin and scale counts, facultative air-breathing, the listed maximum of 28 cm TL and IUCN Least Concern.
• Wikipedia: Guinean bichir: maximum length of 72 cm, greenish-brown to black colour with large dark blotches, slightly protruding lower jaw in mature fish, range from Guinea-Bissau to Nigeria and the naming after William John Ansorge.
• AquaInfo: Polypterus ansorgii, Guinea bichir (Patrick de Pijper): species article by Patrick de Pijper: maximum of up to 90 cm (and why 28 cm is wrong), temperature and pH, starter tank size, layout, escape risk, sharp rear finlets, sensitivity to medication, lifespan, foods, temperament and tank mates.
• Seriously Fish: Polypterus endlicherii: saddled bichir profile used for the size class: maximum 75 cm, adult tank footprint of 210 x 120 cm, floor space over depth, water values, foods and tank mates for a large lower-jawed bichir.
• Seriously Fish: Polypterus senegalus: Senegal bichir profile used as the genus baseline: water values, tight cover, soft substrate, need for atmospheric air, poor eyesight and feeding by smell, anal-fin sexing and care of wild-caught imports.
• OATA: How to look after very large / tankbuster fish: UK trade guidance for very large aquarium fish: tank volume, water-quality limits, filtration, weekly water changes, feeding, acclimatisation and never releasing fish.
• OATA: How to look after wild-caught freshwater fish: UK trade guidance for wild-caught freshwater fish: quarantine, dim lighting, first foods and drip acclimatisation.
• Tropical Fish Co delivery policy: current dispatch days and Live Arrival Guarantee terms.