What Are Polypterus Fish?
Polypterus (Polypterus) are ancient fish that inhabit rivers and wetlands in central-west Africa. Their distinctive silhouette is characterized by a dorsal fin divided into multiple flag-like segments, and they are living fossils that have existed on Earth since before the Cretaceous period.
They possess a modified swim bladder that allows air breathing, and their behavior of surfacing to breathe air can be observed. Due to this characteristic, they are relatively resilient to water quality deterioration and are popular as ancient fish that are easy to keep even for beginners.
The body surface of polypterus is covered with hard scales called ganoid scales, which help build a more robust body compared to other tropical fish. Their eyesight is not highly developed; instead, they use sensory organs on their snout and their lateral line to detect their surroundings and locate food. They have a strong nocturnal tendency and often remain motionless in shadowy spots during the day, with active movement observed during periods when lighting is reduced.
Major Types and Characteristics
Endlicheri is the most popular polypterus species, growing to approximately 50–75 cm in length. They are characterized by beautiful black and brown banding, a gentle temperament, and ease of care. With abundant availability and reasonable pricing, they are ideal as an introductory species.
Senegalus is one of the smallest species, reaching approximately 35–40 cm in length. This small species features a silver base with black spots, and its compact size makes it suitable for keeping multiple individuals.
Ornatipinnis is a large species with striking black and white contrast, reaching 60–80 cm in length. It tends to be somewhat more nervous and territorial than endlicheri.
Delhezi is a beautiful medium-sized species (40–55 cm in length) covered entirely in fine reticulated patterns, with a relatively calm temperament suitable for community aquariums.
Regardless of species, the basic approach to care is largely the same, and all share high adaptability to water quality. When introducing them, providing ample tank space based on their mature size will make long-term care easier.
Tank Size and Husbandry Environment
Since polypterus swim by crawling along the bottom, a tank with a wide horizontal footprint is appropriate. Senegalus require a 90 cm standard tank, endlicheri require 120 cm or larger, and large species require 150 cm or larger.
Fine sand (aquarium sand, bottom sand, etc.) is preferable for substrate, as sharp gravel can injure the belly. Use a top filter or external filter capable of handling the significant ammonia load typical of large fish.
A tank lid is essential. Polypterus can escape at night and will slip out through even small gaps.
Polypterus tend to dislike strong water currents, so directing the filter outlet toward the wall or moderating the flow helps them settle in comfortably. Providing a layout with a wide floor area reduces territorial conflicts when keeping multiple individuals. Placing the tank in a quiet location away from direct sunlight and vibrations minimizes stress on the fish.
Food Types and Feeding Frequency
Polypterus are carnivorous and locate food primarily by smell. Sinking pellet foods (such as Carnival and Crest) are the foundation of their diet. Many individuals initially prefer live food, so switching to pellets requires training.
Frozen bloodworms, frozen crickets, and frozen killifish can be used as live or frozen foods. Care should be taken with live fish as they carry the risk of introducing pathogens. Feeding frequency is generally 3–4 times per week.
When training polypterus to accept pellets, an effective method is to use tweezers to bring the food close to their snout and allow them to smell it before releasing it. While some individuals take time to adjust, persistence will result in most eating pellets. Uneaten food degrades water quality, so it is important to estimate the amount they will eat and promptly remove any leftovers.
Tank Mate Precautions
Polypterus will eat any fish small enough to fit in their mouth. Fish smaller than half their body length are at risk. They can coexist relatively problem-free with large catfish species (such as red-tailed catfish or tiger shovel-nose) or arowanas of similar size.
Tetras, killifish, goldfish, and small characins will almost certainly be predated upon. When keeping multiple individuals of the same species, competition for food can result in torn fins or injured eyes, making a spacious tank and ample hiding places necessary.
Even among the same species, dominance hierarchies can develop based on introduction timing and individual variation, sometimes resulting in torn fins. When adding new individuals, it is advisable to reset the environment by adding hiding places or rearranging the layout, then carefully observe behavior for some time.
Water Quality and Environmental Setup
Since polypterus inhabit African freshwater, they are hardy fish relatively tolerant of poor water conditions.
| Parameter | Target Range |
|---|
| Water Temperature | 24–28°C |
| pH | 6.8–7.8 |
| Hardness | Moderately Hard (GH 8–15) |
| Ammonia / Nitrite | 0 ppm |
Substrate Selection
Since polypterus swim by crawling along the bottom, providing substrate reveals their natural behavior. Fine-grained Ōiso sand and silica sand are ideal. Since they have a habit of burrowing into sand, provide a depth of approximately 5–8 cm.
Driftwood and Rock Placement
Providing multiple hiding places reduces stress. Since polypterus prefer dark crevices, cave-like hiding places created by arranging driftwood are preferred.
Water Change Routine
Since polypterus grow into large carnivorous fish, waste production increases proportionally with feeding amount, making water quality degradation easier. Establishing regular water changes and filter cleaning, while monitoring ammonia and nitrite levels, is key to long-term care. Sudden water quality changes cause significant stress to fish, so it is advisable to bring new water temperature as close as possible to the existing tank water before performing changes.
Health Management and Disease
Polypterus are hardy fish, but they react sensitively to water quality deterioration.
Common Health Issues
- Fungal infection (water mold): Cottony growth on the body. Caused by water quality problems. Treat with Green F Gold.
- Ich (white spot disease): Develops from sudden temperature changes or stress. Treat with medications such as Hikosan Z.
- Rickets-like deformity: Caused by calcium or vitamin deficiency. Prevent through dietary diversity.
Do not obstruct air breathing: Ensure access to the water surface. Strong water currents that cause surface turbulence can make air breathing difficult.
When introducing a new individual, observing its health in a separate quarantine tank before adding it to the main tank helps prevent disease introduction. Habitually observing changes in appetite, body coloration, and swimming behavior, and checking water quality promptly when abnormalities are noticed, helps prevent symptoms from worsening.
Points to Check When Purchasing
Selecting a healthy individual greatly impacts subsequent care. Before purchasing, check for injuries or white spots on the fins or body surface, irregular breathing, and feeding response for peace of mind. After purchase, perform acclimation, gradually introducing the fish to the new environment while avoiding sudden temperature and water quality changes—this supports long-term health.
Summary
Polypterus, with their mysterious appearance characteristic of ancient fish and relatively hardy constitution, are ideal fish for those new to keeping large species. Start with a single senegalus or endlicheri in a 90–120 cm tank to experience their appeal. With proper environment and feeding, they will become long-lived companions living 10–20 years or more.
