Polypterus delhezi is one of the most popular bichir species, prized for its striking banded pattern and manageable size for home aquarium keeping.
Overview
Polypterus delhezi is one of the most sought-after bichir species among aquarists, and for good reason. The combination of a relatively manageable size (35-40 cm), a striking banded pattern, and an ancient, prehistoric appearance makes this fish a true gem in any collection. Native to the Congo River basin in Central Africa, this species inhabits slow-moving rivers, backwaters, and swampy areas with abundant vegetation.
Like all members of the family Polypteridae, Polypterus delhezi possesses primitive lungs that allow it to breathe atmospheric air. You will regularly observe the fish rising to the surface to take a gulp of air — this is perfectly normal behaviour and essential for its survival. The body is covered in tough ganoid scales resembling bony armour, giving the fish a truly prehistoric look. The distinctive dorsal fin is divided into numerous separate spines, a hallmark feature of the entire Polypterus genus.
With proper care, Polypterus delhezi lives 15-20 years, making it a long-term companion for the dedicated aquarist. By nature, it is a nocturnal predator with poor eyesight that relies primarily on its sense of smell.
Tank Requirements
Keeping Polypterus delhezi requires an aquarium of at least 300 litres. Although these fish are not particularly active during the day, they need sufficient floor space to move around during the night. Tank length matters more than height — choose tanks at least 120 cm long.
A critically important point: the aquarium must be fitted with a tight-fitting lid. Bichirs are capable of squeezing through the smallest gaps and can survive outside water for some time thanks to their primitive lungs. All openings for equipment must be sealed.
Optimal water parameters:
- Temperature: 24-28°C
- pH: 6.5-7.5
- General Hardness (GH): 5-20
Fine sand works best as a substrate — bichirs spend much of their time on the bottom and can injure their ventral surface on coarse gravel. Be sure to provide plenty of hiding places: driftwood, ceramic tubes, and rock formations. During the day, Polypterus delhezi prefers to hide, and having adequate shelter significantly reduces stress. Lighting should be subdued; under bright light, the fish will feel uncomfortable and rarely emerge from cover.
Filtration should be powerful but without creating a strong current. Bichirs are inhabitants of calm waters, and a strong flow does not suit them. Remember to leave an air gap between the water surface and the lid — the fish requires access to atmospheric air.
Feeding and Diet
Polypterus delhezi is a dedicated predator, and its diet should reflect this. In the wild, it hunts small fish, crustaceans, worms, and insect larvae.
In the aquarium, the staple diet can include:
- Frozen bloodworms and glassworms
- Shrimp (fresh or frozen)
- Pieces of fish fillet (tilapia, pollock)
- Live or frozen earthworms
- High-quality sinking pellets designed for carnivorous fish
It is best to feed bichirs in the evening or at night when they are most active. Due to their poor eyesight, they rely on scent to locate food, so offerings should be sufficiently aromatic. Not all individuals accept sinking pellets readily — the conditioning process can take several weeks.
Feed juveniles daily; adults should be fed 3-4 times per week. Overfeeding is undesirable as bichirs are prone to obesity when given excess food. Make sure the food actually reaches the bichir rather than being intercepted by faster-moving tank mates.
Care and Maintenance
Keeping Polypterus delhezi is not particularly demanding as long as basic guidelines are followed. Weekly water changes of 20-30% are necessary to maintain stable water quality. When performing water changes, ensure the fresh water matches the aquarium temperature — sudden temperature swings cause stress in bichirs.
Regularly check the integrity of the tank lid and ensure there are no gaps. This is no exaggeration — bichirs are remarkably persistent in their attempts to escape, especially during the first few weeks after introduction or when water quality deteriorates.
Pay attention to skin health. Polypterus delhezi can be susceptible to bacterial infections when kept in polluted water. These fish are also sensitive to elevated concentrations of medications, especially copper-based treatments — if treatment is necessary, use half the recommended dosage.
Bichirs periodically shed a thin film from their entire body surface. This is a normal physiological process that requires no intervention.
Compatibility
Polypterus delhezi has a moderate temperament, but its predatory nature must be considered when selecting tank mates. Any fish that fits into the bichir's mouth will eventually be eaten — it is only a matter of time.
Suitable tank mates:
- Other bichir species of comparable size, such as Nile Bichir or Endlicheri Bichir
- Large catfish (Synodontis, Plecostomus)
- Large peaceful cichlids
- Large characins
- Stingrays (in appropriately sized tanks)
Avoid keeping with:
- Small fish (neons, guppies, small tetras) — they will be eaten
- Aggressive cichlids capable of damaging fins
- Fin-nipping species (some barbs)
When keeping multiple bichirs together, ensure each individual has its own hiding spot. Territorial conflicts are rare but can arise when space is limited.
Breeding
Breeding Polypterus delhezi in captivity is a challenging but achievable task for an experienced aquarist. In the wild, spawning coincides with the rainy season, which is associated with changes in water parameters and an increase in food availability.
To stimulate spawning:
- Gradually lower the temperature by 2-3°C, then slowly raise it to the upper end of the range (27-28°C)
- Increase the frequency of water changes using soft, slightly cooler water
- Feed the breeding pair generously with live foods for 2-3 weeks
During spawning, the male forms a cup-like shape with his anal fin, into which the female deposits eggs. The male then fertilises the eggs and scatters them among fine-leaved plants or synthetic spawning mops. After spawning, the adults must be removed, as they will readily consume their own eggs.
Incubation takes 3-4 days at 26-28°C. The larvae initially feed on their yolk sac, after which they can be transitioned to brine shrimp nauplii and microworms. Fry grow slowly, and during the first few months it is important to sort them by size — larger individuals may prey on their smaller siblings.