Bichirs are African freshwater fish in the family Polypteridae. Their long bodies, tough scales and rows of dorsal finlets give them a prehistoric look—and the nickname “dinosaur fish”—but they are living fish, not dinosaurs or eels. Some species are kept in aquariums, where their adult size, predatory habits and need for surface access make careful species identification essential.
What is a bichir?
A bichir is a member of the fish family Polypteridae, a group native to Africa. WWF describes 14 bichir species in its account of African freshwater fish; the species do not all have the same range, appearance or adult size. They are sometimes called “dinosaur fish” because their bodies and fins look unusual beside those of many familiar aquarium fish. WWF also uses the phrase “living fossils,” but that is a descriptive nickname, not a precise scientific classification or proof that modern bichirs have remained unchanged for a particular span of time.
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The name Polypterus means “many fins,” according to the specialist aquarium guide, and refers to the separate finlets running along the back. Bichirs are ray-finned fish with distinctive anatomy and behavior. Their resemblance to an eel comes mainly from their elongated shape; it does not make them eels.
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The nickname is useful shorthand for their striking appearance, but it can create the wrong expectations. A bichir is not a dinosaur, and “dinosaur fish” does not identify a particular species or indicate a particular adult size. If you are considering one for an aquarium, the scientific name matters more than the nickname: a small-looking juvenile may belong to a species that eventually needs a much larger footprint than the fish’s current size suggests.
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What makes bichirs look and behave differently?
Dorsal finlets, pectoral fins and armor-like scales
A bichir’s back is lined with a series of small dorsal finlets rather than one continuous dorsal fin. Its broad, fleshy pectoral fins are prominent and help it move. The body is covered in tough ganoid scales, which contribute to its armored appearance. These features, combined with a long body and a low-slung way of moving, explain why the fish looks so unlike the typical aquarium species.
How bichirs breathe at the surface
Bichirs have a modified, two-part swim bladder that functions in a lung-like way. They can rise to the surface and gulp air in addition to using their gills. In an aquarium, that means the route to the surface must remain open: do not seal the water beneath a lid or arrange decorations so the fish cannot reach the air. Leave an air gap between the waterline and cover.
This breathing behavior also explains why a secure cover must be fitted without blocking surface access. Bichirs can escape through gaps, so a tight-fitting, heavy cover is a practical safety measure. It should close securely while still leaving the fish room to reach the surface beneath it.
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1Scan for outdated or missing drivers - takes under a minute2Repair Windows errors before they cause bigger problems3Fix the driver behind crashes, sound loss and screen glitchesSurface access and escape prevention are two requirements to meet together, not alternatives. A cover that leaves a large opening may make it easy for the fish to reach air but also leave an escape route; a cover pressed down so tightly that it eliminates the air gap would not meet the fish’s surface-breathing needs. Arrange the tank so the bichir can move freely from the bottom to the surface while the lid remains secure around the tank and equipment.
Where do bichirs live in the wild?
Bichirs are African freshwater fish. The WWF report describes the 14 species in its account as restricted to Africa, but their habitats and distributions vary. Broad habitat descriptions include rivers, streams, shallow floodplains, swamps and lakes. It would be misleading to assume that every species lives in the same kind of water or occupies the whole continent.
For example, the CLOFFA entry for Polypterus bichir lists the Nile, Chad, Niger, Volta and Senegal systems, several West African coastal basins and part of the Congo basin. By contrast, a U.S. Fish and Wildlife Service risk screening describes P. delhezi from the middle Congo basin. These are species-specific records, not a range map for all bichirs.
A species-specific example: Polypterus bichir
CLOFFA characterizes P. bichir as essentially piscivorous, meaning it primarily eats fish, while also taking crustaceans. Its account describes flood-season spawning: adults enter floodplains, eggs are deposited among weeds, and the adult guards them. That description applies to the species covered by the entry; it should not be treated as a universal account of reproduction across the family.
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This example also shows why a family-level description should not be mistaken for a complete account of every species. A range or breeding note for P. bichir is useful when discussing that fish, but it does not establish that all bichirs have the same spawning behavior or occupy the same river systems. Species identification gives context to both natural-history details and aquarium planning.
How big do bichirs get?
There is no single adult-size estimate that applies to every bichir. The specialist aquarium guide says even smaller species may reach about 25–30 cm in aquariums, while some exceed 60 cm. WWF says larger species can grow up to 1 m. These broad figures are a reason to identify the species before choosing a tank, not a prediction that every bichir will reach the largest reported size.
| Fish or source statement | Reported measurement | How to interpret it |
|---|---|---|
| Larger bichir species, WWF | Up to 1 m | General upper figure for larger species in WWF’s account; not a size for every species. |
| Polypterus bichir, CLOFFA | 750 mm standard length; 820 mm total length | Species entry accessed in 2026. Standard length and total length are different measurement conventions. |
| Polypterus delhezi, FishBase figure reproduced in a 2021 U.S. Fish and Wildlife Service screening | 44.0 cm total length | The screening cites Froese and Pauly (2018); this is a reported record, not a guaranteed adult size for every specimen. |
| Smaller species in aquariums, Polypterus.info | About 25–30 cm | Specialist aquarium-guide estimate; some bichirs grow beyond 60 cm. |
The values in the table describe different species, sources and measurement conventions. Standard length does not include the tail in the same way total length does, so those measurements should not be compared as though they were measurements of the same fish. When buying a juvenile, plan around its identified species and potential adult size rather than its current length.
Size is not just a question of how long the fish looks in a display tank. It determines how much usable bottom area to provide and whether current tankmates are likely to remain suitable. A general maximum for “bichirs” cannot tell you whether a specific aquarium is large enough: match the particular fish to species-level size information where possible, and allow for the number of fish you intend to keep.
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Outbyte Driver Updater FREEScan for outdated or missing drivers - takes under a minuteDriver Scan →Outbyte PC Repair FREERepair Windows errors before they cause bigger problemsFix Now →Longevity also depends on the source and the conditions being described. WWF gives a figure of up to 30 years in captivity. Petco’s 2024 retailer care guidance gives a range of 10–20-plus years with proper care. These are care-reference estimates, not results from a controlled lifespan study. They both underline that keeping a bichir can be a long-term commitment.
What should you know before keeping a bichir?
Identify the species and plan for its adult footprint
Tank dimensions should follow the species, its expected adult size and the number of fish—not a generic label such as “dinosaur fish.” Polypterus.info offers these footprint recommendations for its setup guidance:
| Setup described by Polypterus.info | Suggested footprint | Context in the guide |
|---|---|---|
| Smaller species and ropefish | At least 122 × 38 cm | A minimum footprint in that specialist guide. |
| A group of small-to-medium bichirs | 153 × 46 cm | Described as a more suitable base for a group. |
| Larger forms, including ornate, endlicheri and the P. bichir complex | 183 × 61 cm | Described as more appropriate for these larger forms. |
These are recommendations from one specialist husbandry source, not a universal standard or a guarantee that a tank is suitable in every setup. The guide emphasizes floor area over height: a broad base gives a bottom-oriented fish more usable space. Consider the eventual adult length, the number of fish, and how much unobstructed bottom area remains after adding equipment and décor. If the fish’s identity is uncertain, resolve that before relying on a size-specific tank recommendation.
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As the setup guide puts it, “The size of the base area is much more important than the height of the tank, so opt for a shallower tank with a large footprint where possible.” That is a practical comparison to keep in mind when considering tanks with similar capacity but different shapes. A tall aquarium does not automatically provide the same usable floor area as a broad one. Measure the base and think about the space left for the fish to move along the bottom rather than choosing by height alone.
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The listed dimensions are best treated as starting points for matching a footprint to the broad size category in that guide. They do not erase the need to confirm the species, consider adult size and number of fish, or account for the tank’s layout. In particular, a recommendation for a group is not interchangeable with a recommendation for one fish, and the guide’s figures should not be turned into a guarantee that every tank of those dimensions will suit every bichir.
Keep the surface reachable and the tank escape-proof
Arrange the waterline and cover so the fish can rise for air, and leave the air space beneath the cover. Close gaps around the lid and equipment. Because bichirs can escape, a loose or incomplete cover is not a safe substitute for a correctly fitted one. At the same time, do not create a sealed enclosure that prevents access to the surface.
Choose substrate with cleaning in mind
Polypterus.info recommends fine, aquarium-marketed sand as a practical option. Fine sand can be easier to keep clean than gravel in the guide’s account, while gravel may conceal waste and can be swallowed accidentally. Sand is optional rather than a biological requirement established by these sources; the useful decision is to select a safe substrate that you can maintain and that suits the fish and tank layout.
Choosing aquarium-marketed sand is an optional product decision, not a special brand requirement. The practical point is the substrate’s texture and how it affects cleaning: the specialist guide presents fine sand as straightforward to maintain, while noting the potential drawbacks of gravel. Whichever option you choose, consider the fish’s bottom-oriented habits and whether waste will be easy to see and remove.
What do bichirs eat?
Bichirs are predators and often use smell to find food. The aquarium-care references describe them as opportunistic carnivores. Examples listed by Polypterus.info include cockle, mussel, shrimp, baitfish, sinking catfish pellets and smaller frozen foods such as bloodworm. Petco’s care sheet also lists animal-based frozen, freeze-dried or live foods and carnivorous pellets.
These are examples from aquarium-care references, not a complete veterinary nutrition prescription. Avoid basing the entire diet on one item simply because the fish accepts it. Offer a varied diet appropriate to the fish’s size and feeding response, and use sinking foods when needed to get food to a fish that feeds near the bottom. Remove uneaten food so it does not remain to foul the aquarium.
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The mix of examples matters: care references include both whole or prepared animal foods and carnivorous pellets, rather than prescribing a single product. A sinking pellet can be one part of the diet, but it should not be treated as evidence that every bichir will eat the same food or that one item supplies everything it needs. Match food size to the individual fish and pay attention to whether it is actually finding and eating what you offer.
Because bichirs may locate food by smell and feed opportunistically, a tankmate that appears safe during the day may still be at risk when resting. Small fish, especially those that settle near the bottom at night, can be eaten. A fish’s current size is not enough to judge safety: consider whether it could fit into the bichir’s mouth as the bichir grows.
Which fish can live with bichirs?
Compatibility is conditional, not guaranteed by a species list. A sensible starting point is to avoid tankmates small enough to swallow and fish so aggressive that they are likely to injure or relentlessly harass the bichir. The specialist guide also warns that some suckermouth catfish may harass bichirs. Petco lists a broader set of potentially suitable fish of similar size, but any such pairing still depends on individual fish, the available space and the specific bichir.
- Compare adult sizes, not just the sizes of fish at the shop. A tankmate must remain too large to swallow as both fish grow.
- Assess temperament and feeding competition. A much more aggressive fish may cause stress or injury even if it cannot eat the bichir.
- Watch for nighttime risk. Small, bottom-resting fish can be vulnerable while the bichir is active or searching for food.
- Check compatibility for the actual species and setup. A general claim that two fish “get along” is not a guarantee for every individual.
Use size and temperament as the first filter rather than treating any suggested tankmate list as a promise. A similarly sized fish may be a possible candidate in a care guide, but the actual pairing still depends on the bichir’s species, the other fish’s adult size and behavior, and the room available. If the tankmate is small enough to be swallowed, its being peaceful or compatible today does not remove the risk as the bichir grows.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.How to choose a bichir responsibly
There is no single best bichir for every aquarist. The most useful comparison begins with whether the fish’s adult requirements fit the aquarium and the keeper’s long-term plans. Appearance matters, but a striking pattern is not a substitute for identifying the species and understanding its size.
- Confirm the species name. Ask for the scientific name and check that the seller’s identification is credible. Common names can be imprecise, and different species have different ranges and adult sizes.
- Check the likely adult length. Use species-specific information where available. Broad family-level numbers—from 25–30 cm for smaller aquarium species to more than 60 cm for some, and up to 1 m for larger species—are not interchangeable predictions.
- Match the fish to floor space. Compare the tank’s usable footprint with species-appropriate guidance. Leave enough open bottom area after accounting for furnishings and equipment.
- Consider the existing fish. Assess adult mouth size, temperament and nighttime vulnerability rather than relying on a blanket tankmate list.
- Plan for the whole setup. Make sure the tank has a tight cover, a clear route to the surface, an air gap and a substrate you can maintain.
- Think beyond purchase day. Care references describe bichirs as potentially long-lived, with estimates ranging from 10–20-plus years in Petco’s 2024 guidance to up to 30 years in WWF’s account.
A comparison between bichirs should therefore begin with adult length and the tank footprint that follows from it, not a blanket claim that one species is “best.” Geographic origin can help distinguish what species an account describes; confidence in the identification matters because a label affects how useful size and range information will be. Appearance can be part of the choice—the ornate form is one example of a named larger type in the setup guide—but looks do not tell you whether its eventual size fits your aquarium.
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Trade availability is another consideration when comparing species, but the cited accounts do not establish a dependable ranking of availability or provide current prices. Do not let a commonly used trade name stand in for a verified identification. Similarly, no universal ranking of beginner-friendliness, temperament or ease is established by these sources. A responsible decision rests on a confirmed species, realistic adult-size expectations, adequate floor area and tankmates that remain appropriate as the fish grow.
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For a species-level comparison, consult a dependable identification source and distinguish between documented range, reported maximum or record length, and aquarium-care estimates. The sources available here do not establish a universal ranking of species by ease, temperament or suitability for beginners, so those claims should not drive a purchase decision.
Sources and what their figures mean
WWF provides a broad overview of African bichir diversity and natural history. CLOFFA supplies a species entry for P. bichir, while the U.S. Fish and Wildlife Service screening gives context for P. delhezi and reproduces a FishBase length figure. Polypterus.info is a specialist aquarium source for practical setup and behavior; its tank dimensions are source-specific recommendations. Petco’s care sheet is retailer guidance, including its feeding and lifespan estimates.
- WWF, Africa’s Forgotten Fishes: 1. Dazzling Diversity
- Polypterus.info, Keeping Polypterus (Bichirs) in the Aquarium
- Polypterus.info, Polypterus (Bichirs) Tank Setup
- CLOFFA / Royal Museum for Central Africa, Polypterus bichir Lacépède, 1803
- Petco, Bichir Care: The Ultimate Guide to Your Dinosaur Aquarium Fish (updated August 12, 2024)
- U.S. Fish and Wildlife Service, Ecological Risk Screening Summary: Barred Bichir (Polypterus delhezi), 2021
Frequently Asked Questions
Are bichirs dinosaurs or eels?
No. Bichirs are living African freshwater fish in the family Polypteridae. “Dinosaur fish” is a nickname for their unusual, prehistoric-looking bodies and fins; their elongated shape may resemble an eel, but they are not eels.
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They use gills and can also rise to gulp air using a modified, lung-like swim bladder. Keep a clear path to the surface and an air gap beneath a secure, tight-fitting cover.
How large does a bichir get?
It depends on the species. A specialist aquarium guide says even smaller species may reach about 25–30 cm in aquariums and some exceed 60 cm; WWF reports that larger species can grow up to 1 m. Identify the fish before choosing its tank.
What do bichirs eat, and can they live with other fish?
Care references list animal-based foods such as shrimp, mussel, baitfish, frozen foods and carnivorous pellets. Bichirs are predators, so small fish—especially fish resting near the bottom at night—may be at risk. Tankmates should be too large to swallow and not so aggressive that they harass the bichir; compatibility is never guaranteed by a general list.
How long can a bichir live in captivity?
WWF gives an estimate of up to 30 years, while Petco’s 2024 retailer care guidance says 10–20-plus years with proper care. These are care-reference estimates, but both suggest that keeping a bichir can be a long-term commitment.
The Bottom Line
Bichirs are African predatory fish with distinctive dorsal finlets and a modified swim bladder that lets them gulp air at the surface. The nickname “dinosaur fish” does not identify a species, and adult sizes vary widely. Before choosing one, confirm its identity, plan around its adult size and tank footprint, preserve surface access under a secure cover, and consider carefully whether its tankmates will remain safe.
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