Senegal Bichirs and Ropefish Reward Space, Security, and Thoughtful Tankmate Choices
Polypterids and ropefish are hardy for their niche, but they are still specialized predators that need secure covers, meaty diets, and tankmates too large to be swallowed.
A safer setup path for bichirs and ropefish
Care Factor
| Care Factor | Senegal Bichir / Ropefish Need | Why It Matters | Common Beginner Mistake |
|---|---|---|---|
| Tank design | Long tank with resting room and cover | These fish cruise the bottom and surface rather than using tall water columns efficiently | Buying a tall tank with limited footprint |
| Tankmates | Robust fish too large to fit in the mouth | Prevents predation and chronic stress | Mixing with tiny tetras, guppies, or shrimp |
| Security | Tight-fitting lid and blocked equipment gaps | Ropefish especially are famous escape artists | Leaving cable holes or loose lids open |
| Feeding style | Meaty, species-appropriate foods offered consistently | Supports condition without frantic competition | Assuming they will thrive on random community leftovers |
Bichir and Ropefish Setup Checklist
| Use a secure lid with every opening blocked or taped safely | |
| Provide hides, plants, or driftwood so the fish can rest out of harsh light | |
| Choose tankmates that are calm, not tiny, and not likely to nip | |
| Expect them to treat very small fish or crustaceans as prey | |
| Assume eel-like appearance means they want brackish conditions by default | |
| Keep them in uncovered tanks because they stay on the bottom |
These fish often do best in calm, secure aquariums where the aquarist plans for their predatory nature before stocking the rest of the tank.
A bichir or ropefish missing from the tank should trigger an immediate lid-and-floor search. Escapes happen quickly and often through surprisingly small gaps.
Bichirs (family Polypteridae) are some of the most ancient fish in the aquarium hobby -- ray-finned fish whose lineage diverges from other actinopterygians over 400 million years ago, closer in anatomy to ancient lobe-finned fish than to modern teleosts. The Senegal bichir (Polypterus senegalus) and the ropefish (Erpetoichthys calabaricus) are the two most commonly available species. Both breathe air using a primitive lung, have armored scales, and are night hunters of small fish and invertebrates.
| Species | Adult Size | Min. Tank | Key Risk |
|---|---|---|---|
| P. senegalus (Senegal Bichir) | 12–14 in | 55 gal | Lid gaps; eats small tankmates |
| E. calabaricus (Ropefish) | 15–24 in | 75 gal | Extreme escape risk; seal every gap |
The Polypterid Body Plan
Bichirs have elongated bodies covered in ganoid scales -- interlocking rhomboid plates of a hard material (ganoin) that functions as armor. The dorsal fin is divided into a series of finlets -- small, individually supported spines running along the back -- which gives them a prehistoric, dragon-like silhouette. The pectoral fins are lobed and muscular, used for crawling along the substrate.
The ropefish is the most eel-like member of the family -- extremely elongated, with reduced pelvic fins and a sinuous swimming style. Despite the dramatic difference in body shape, it shares the same care requirements and behavioral traits as Polypterus species.
Air Breathing
Both bichirs and ropefish breathe air through a modified swim bladder that functions as a lung. They must have access to the surface to breathe air -- they will drown in a sealed aquarium. Tank lids must have gaps or mesh areas at the surface. In well-oxygenated water they breathe air less frequently; in low-oxygen water they surface more often. Do not keep in a sealed container or tightly covered tank.
Tank Requirements
A single adult Senegal bichir (reaching 12--14 inches) needs a 55-gallon tank minimum; ropefish (reaching 15--24 inches) need 75 gallons. Both are escape artists of the highest order -- ropefish in particular will find any gap in a lid, any drain tube, or any overflow. All openings must be sealed with mesh; ropefish routinely desiccate on the floor after escaping overnight. Use a tight-fitting lid.
Both species are nocturnal and prefer hiding spots -- caves, PVC tubes, and driftwood tangles. A sandy substrate allows bichirs to half-bury themselves during the day. Temperature: 74--82 degrees F. pH: 6.5--8.0. Both are tolerant of a wide range of water chemistry.
Feeding
Senegal bichirs and ropefish are carnivores with poor eyesight but excellent smell. They hunt by scent at night. Feed meaty foods: earthworms, shrimp, krill, bloodworms, small fish pieces, and carnivore pellets. They do not reliably find floating pellets -- sinking pellets placed near them after lights-out work better. Live feeder fish should be avoided due to parasite risk; gut-loaded feeder shrimp or earthworms are safer.
Tankmates
Both species are peaceful toward fish too large to swallow but will eat anything that fits in their mouth -- and a bichir's mouth is wider than it looks. Keep with fish of equal or greater size. Known good tankmates: large cichlids, large catfish (plecos, synodontis), large danios, and other robust fish. Do not keep with fin-nipping species, as bichir fin tips are soft and susceptible to damage.
Health
Head and lateral line erosion (HLLE) occurs in poor water conditions. Bacterial infections affect the ganoid scales and soft fins. Maintain water quality with regular partial water changes (30% weekly). Ropefish are particularly sensitive to ich treatments containing copper -- use copper-free medications at half dose for scaleless fish protocols.
Sources: Cloutier & Ahlberg (1996), "Morphology, characters, and the interrelationships of basal sarcopterygians," in Interrelationships of Fishes; FishBase species accounts P. senegalus and E. calabaricus; Reed & Paller (2005) Congo basin ichthyology; Practical Fishkeeping bichir husbandry guides.