Bichir: Ancient Air-Breathing Fish for Home Aquariums

A bichir is a primitive freshwater fish from the Polypteridae family, native to African rivers and floodplains, recognized by a row of small dorsal finlets, armor-like ganoid scales, and a serpentine body that can fool the eye into seeing an eel. What separates it from nearly every other common aquarium fish is a pair of functional lungs, an inheritance from a lineage more than 400 million years old, which means the animal must surface to gulp air or it will literally drown. That single fact shapes every decision you make as a keeper.

This guide covers the basics of keeping a bichir, from identifying the most common species and planning tank setup to feeding routines, compatible tankmates, and the long-term commitment these air-breathing fish demand.

Meet the Bichir, a Living Fossil From Before the Dinosaurs

The Polypteridae family tree is older than dinosaurs by a wide margin. Fossil relatives appear in Devonian deposits more than 400 million years old, roughly 200 million years before the first dinosaur walked on land. The bichir you bring home is, in a real sense, a swimming relic, an amphibious fish whose body plan has been tested by time in a way no other common aquarium pet can match.

Several anatomical details explain why bichirs are instantly recognizable and frequently misidentified. Their body is covered in hard, diamond-shaped ganoid scales that feel closer to chainmail than to the flexible scales of a typical fish. A row of small, individual dorsal finlets runs along the back instead of one continuous dorsal fin. The head is broad and flat, and the pectoral fins work almost like tiny paddles, letting the fish crawl along the substrate. These features are why newcomers sometimes call them dragon fish, dinosaur eels, or armored eels, even though they are neither eels nor related to dinosaurs at all.

“Side note: the nickname “dinosaur bichir” comes from this body plan, not from any direct link to dinosaurs. The fish sits on the early tetrapod branch that eventually gave rise to land vertebrates.

The single most important anatomical fact is the lung system. Bichirs have paired lungs connected to the esophagus, a primitive arrangement that sets them apart from most modern fish, which rely on gills and a swim bladder for buoyancy. Because these lungs evolved before the swim bladder became a gas-regulating organ, its can drown if they cannot reach the surface. Young its also develop external gills as juveniles, looking almost like tiny axolotls, and they lose those external gills as they mature into air-breathing adults. This combination of lungs, external juvenile gills, and amphibious tolerance is what makes a it feel closer to a salamander than to a guppy.

Popular Bichir Species and How They Compare in Size and Temperament

Most its sold under the catch-all label “it fish” come from a small handful of Polypterus species, and the difference between them is the difference between a manageable pet and a tank-busting commitment.

Beginner-Friendly Species Under 18 Inches

The Dinosaur it (Polypterus senegalus) is the species almost every hobbyist starts with. Adults reach roughly 12 inches, tolerate a wider range of water conditions than their larger cousins, and accept prepared foods more readily. The Saddleback it (Polypterus endlicherii) is the next step up, topping out around 18 to 24 inches, with a calmer temperament and a slightly thicker body. Both are reasonable choices for a first-time keeper, provided the tank is large enough.

Larger Showpiece Species

The Ornate it (Polypterus ornatipinnis) is the species most people picture when they search for a it for sale online. It carries bold, lacy patterning on the fins and face, and adults commonly reach 18 to 24 inches, with exceptional specimens pushing past 30 inches. The true giants, including Polypterus it (sometimes called the Nile it or the Cahama), can exceed 36 inches in captivity and need aquariums measured in hundreds of gallons.

Matching Species to Experience Level

Use the table below to anchor expectations before you buy. Minimum adult length is what a healthy fish will reach in a properly sized tank, not the size of the juvenile you see in a store. Growth speed matters because fast growers outpace small setups within a year.

Species	Minimum adult length	Growth speed	Handling difficulty
Polypterus senegalus	~12 in	Moderate	Beginner
Polypterus endlicherii	~18-24 in	Moderate	Beginner to intermediate
Polypterus ornatipinnis	~18-24 in	Slow to moderate	Intermediate
Polypterus it (giant)	~30-36 in	Slow but relentless	Advanced

The honest answer to “how big do its get” is simple: bigger than most pet store tanks. A Senegal it fits a 40- to 55-gallon setup, an Ornate or Saddleback belongs in 125 to 180 gallons, and the giants only thrive in custom enclosures of 240 gallons or more.

Bichir Tank Size, Setup, and the Surface-Access Rule

Because its must breathe atmospheric air, every setup decision flows back to a single rule: the fish has to reach the surface easily, in a calm spot, every day, for the rest of its life.

Tank Footprint and Volume by Species

• ▸Senegal it (12 in): a 40-gallon breeder with a 36-inch floor footprint is the practical minimum for a single adult.
• ▸Saddleback or Ornate (18 to 24 in): a 125- to 180-gallon tank with at least 6 feet of floor length.
• ▸Giant Polypterus (30+ in): custom builds of 240 gallons or larger, ideally 8 feet long, because floor footprint matters more than height for a bottom-dwelling fish that walks more than it swims.

Securing the Top and Clearing the Surface

its are escape artists, and a tight-fitting, weighted lid is non-negotiable. Every cord, hose, and filter opening needs a guard or sponge block, because the fish will explore any gap. Leave at least one open breathing lane free of floating plants and surface agitation, so the fish can gulp air without fighting the current or hitting a stem. A calm surface film is a feature, not a flaw, in an African freshwater aquarium built around this species.

Substrate, Décor, and Filtration

Fine sand mimics the slow African river bottoms where Polypterus species evolved and protects the belly as the fish crawls. Smooth driftwood, caves, and broad-leaf plants give a daytime refuge, but skip sharp-edged rock that can scrape those ganoid scales. Lighting should be dim, and filtration should be strong on biological capacity but gentle at the outlet, since heavy current exhausts its faster than it does streamlined swimmers.

Calmer water also changes when and how it hunts, since a tired bichir that cannot fight the current still has to find food after dark.

Feeding a Predatory Nocturnal Hunter by Smell

its have poor eyesight and rely on a strong sense of smell to locate food. Anything that smears scent across the substrate will draw them out, and anything that depends on visual cues will be ignored. That is why it feeding succeeds or fails based on what reaches the bottom in a dark room.

Building a Carnivorous Diet

• ▸Sinking carnivore pellets: the backbone of the diet, because they sink, hold scent, and let a slow eater feed at its own pace.
• ▸Frozen bloodworms and mysis: ideal for juveniles under 4 inches that cannot yet handle bigger prey.
• ▸Frozen krill and silversides: excellent for adults; krill also boosts color in ornate species.
• ▸Raw market shrimp and peeled mussel: a once-a-week protein boost, chopped to mouth size and offered with long tweezers to build trust.

Transitioning Stubborn Juveniles

Newly imported its often refuse anything that does not move. Start with frozen bloodworms offered at night, then mix in a few sinking pellets on the same dish. Over two to three weeks, gradually reduce the frozen portion and increase the pellet share. Starvation is a real risk during this window, so weigh the fish monthly and do not extend the transition past four weeks without a vet check.

Feeding Frequency and the Obesity Risk

Juveniles under 8 inches benefit from daily feeding because they are still building mass. Adults do best on two to three feedings per week, with one fasting day built in. Because its are slow, bottom-dwelling, and almost always hungry, they will accept every meal you offer and quietly become obese in a richly decorated tank. A visibly rounded belly that does not taper into the tail by the next day is the early warning sign. Cut portions before cutting frequency.

“Pro tip: turn off the room lights, drop the food within an inch of the fish’s nose, and wait. A it that ignores food in a bright tank will hunt confidently in the dark, mirroring how it feeds in African rivers at night.

Compatible Tankmates, Behavior Cues, and Long-Term Commitment

The behavior answer comes early: its are peaceful, slow-moving, opportunistic predators. Anything that fits in their mouth becomes food, and anything aggressive enough to outcompete them at the surface becomes a stress source.

Tankmates That Actually Work

• ▸Silver dollars: fast, mid-to-top-level swimmers too big to swallow and too quick to bully.
• ▸Larger gouramis and severums: peaceful, size-matched cichlids that share the it’s calm temperament.
• ▸Larger rainbowfish and Congo tetras: active enough to stay out of the it’s strike zone but peaceful enough not to harass it.
• ▸Other its of similar size: juveniles often cluster, but adults become territorial, so plan tank size up for every additional fish.

Anything smaller than the it’s head is a snack, and that includes neon tetras, adult shrimp, and small cichlids. The answer to “are its aggressive” is more nuanced than a simple yes or no: they are aggressive only toward prey, but they will swallow any tankmate that fits, and they suffer when housed with nippy or hyperactive fish.

Reading Stress Signals

Stress in its is easy to miss because they sit still by default. Refusal to surface for air, clamped pectoral fins, hiding for more than two days, or a sudden burst of daytime activity all point to a problem. Sudden daytime activity in a nocturnal fish is often the first sign of water-quality trouble or bullying, and it should trigger an immediate parameter check.

The Honest Long-Term Picture

Most its live 15 to 20 years in captivity, with well-kept specimens pushing past two decades. That is a longer commitment than most dogs, and the cost picture should be planned in advance. Budget for a heater and filter running 24/7, monthly water changes, regular replacement of filter media, an annual tank upgrade as juveniles grow, and a food bill that scales with the fish’s appetite. Power outages are a special risk because the filter stops, the surface film can break, and the it’s oxygen supply can collapse within hours. A battery-powered air pump on a smart plug is a small, low-cost insurance policy against a 20-year pet.

Troubleshooting the Most Common Bichir Problems

Most “problems” people report are actually normal behavior, and learning the difference saves a lot of unnecessary medication.

When Sitting Still Is Normal

A it that rests motionless on the substrate for hours is almost always asleep, not sick. Watch the secondary signals: gill movement should be slow and steady, the fish should rise to gulp air within 30 minutes of lights-out, and the belly should remain rounded but not bloated. A motionless fish that refuses air for an entire day is a genuine emergency.

Refusal to Eat

Skip the panic medication and run through this checklist first. Confirm that water temperature sits between 76 and 82°F, since cooler water slows digestion. Try a different protein, switching from pellets to frozen bloodworms or vice versa, because scent triggers matter more than brand. Watch for tankmate bullying at feeding time, especially from cichlids that defend the surface. A it that has not eaten for more than two weeks as an adult, or more than four days as a juvenile under 4 inches, needs hands-on intervention.

Escape Attempts

Lower the water level by an inch so the lid is the only obstacle, weigh the lid with books or clips, and block every hose gap with a pre-filter sponge. its climb outlet pipes like ladders, so any vertical hardware near the surface is an open door.

Excessive Surface Gulping

Lungs supply most of a bichir’s oxygen, so occasional surface breaks are routine, yet nonstop gulping, piping, or flared gills usually point to oxygen-depleted or chemically irritated water. Boost surface agitation with an air stone, check ammonia and nitrite to rule out gill burn, and confirm that the heater is not pinned above 84°F, because warmer water holds less dissolved oxygen.

Bottom Line: A it rewards patience, planning, and a steady routine. Choose a species that fits the tank you already own, not the one you hope to buy someday, secure the lid before you fill the water, and feed by scent in a dim room. Done well, this 400-million-year-old lineage settles into a living-room aquarium as calmly as it once patrolled the floodplains of the Nile River, and it will outlast most of the other fish you keep alongside it.

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