Rope fish

Water parameters

Tolerated range for this species. Aim for the middle of each band rather than the extremes.

Tank and habitat

Substrate: sand.

Behavior

Plant interaction: plant safe.

Typically wild-caught; acclimate slowly.

Feeding

Carnivore that prefers live and frozen meaty food. Frozen bloodworm, frozen prawns, frozen mysis, live earthworms, live blackworms, and live feeder shrimp are the core diet. They hunt by smell rather than sight, weaving their body across the substrate to locate food. Pellets are reluctantly accepted by some individuals but many refuse dry food entirely. Feed after lights-out when the rope fish is active. In community tanks, ensure food reaches the bottom before other fish intercept it. Feed every other day for adults; daily for juveniles. They eat slowly and may take 10-15 minutes to finish a meal.

Nocturnal feeder; drop food after lights out.

Compatibility

• Peaceful despite looking predatory. Rope fish ignore tankmates that are too large to swallow, which in practice means anything over 5–6 cm. Small fish (neons, guppies, small rasboras) and shrimp are eaten.
• Best with medium to large peaceful community fish: larger barbs, rainbowfish, medium cichlids, larger tetras, and catfish. Avoid housing with aggressive species that would harass the slow-moving rope fish.
• Nocturnal. They hide during the day and become active at dusk. Expect to rarely see them during daylight hours unless the tank is dimly lit with plenty of hiding spots.
• Escape artists of the highest order. Rope fish squeeze through any opening in the lid, climb filter tubing, and exit through gaps around equipment. Sealing the tank completely is mandatory. They can survive out of water for extended periods by breathing air through a primitive lung, so rescue fish from the floor promptly.

Origin and habitat

Erpetoichthys calabaricus, the ropefish or reedfish, is an elongate, snake-like fish from the coastal rivers and estuaries of West and Central Africa, ranging from the Oueme in Benin to the Sanaga in Cameroon. It is the only species in its genus and belongs to the family Polypteridae, the bichirs, an ancient lineage of ray-finned fish. The genus name comes from the Greek for creeping thing and fish. The body is covered in hard, glossy ganoid scales rather than ordinary fish scales, and it lacks pelvic fins entirely while carrying a row of small separate finlets along the back, which together set it apart from the related bichirs. It is greenish-black above and yellowish below and grows to around 37 cm, with 30 cm or so more typical. Like other polypterids it has a primitive paired lung as well as gills, takes a large share of its oxygen by gulping air at the surface, and can survive for hours out of water as long as it stays moist. It is a nocturnal hunter that tracks prey by smell. IUCN lists it as Near Threatened overall, with higher concern in central Africa.

Breeding

Ropefish are not bred in home aquariums, with only a single reported captive spawning, by a long-established group, decades ago. Fertilisation is internal, unusual for a fish: the male wraps his modified anal fin around the female to form a cup in which a few eggs are fertilised before his tail flicks them away among plants. Spawning in the wild probably happens in flooded vegetation during the rains, and the larvae carry external gills like a salamander's. Sexing is hard, resting on a subtle difference in the anal fin, and the species seems to take many years to mature, so all trade fish are wild-caught.

Common problems

Escaping is the defining problem. A ropefish will find any gap, squeezing its thin body through filter slots, cable holes, and the space behind the lid, and it can breathe air long enough to survive a spell on the floor, so every opening has to be sealed and a stray fish rescued quickly. Many refuse dry food and need live or frozen meals, and in a community tank they can go hungry if faster fish clear the food before the ropefish emerges at night, so after-dark feeding helps. Despite their tough ganoid scales, they are sensitive to poor water quality, and skin or fungal infections set in when conditions slip, so medications are best used cautiously, water kept clean, and the tank given dim light and plenty of cover to reduce daytime stress.

Bioload

Further reading

• How to cycle a fish tank
• Stocking ideas by tank size