Rope Fish Care Guide: Tank Mates, Size & Setup

With its eel-like body, the rope fish appeals to keepers who want something different from the usual community fish.

They’re peaceful carnivores that do well with other large, peaceful fish. That makes them a good fit for species-only tanks and for community tanks, as long as you choose tank mates carefully.

The shape puts some people off, but rope fish are hardy and undemanding once the tank is set up properly. The main challenges are the tank size, the tight lid they need, and the fact that they eat anything that fits in their mouth.

The best rope fish tank mates are fish too big to swallow and calm enough not to bully a slow, nocturnal feeder. Angelfish, bala sharks, large gouramis, clown loaches and Synodontis catfish all fit that description. Avoid tetras, rasboras, danios, shrimp and aggressive cichlids.

Rope Fish Facts & Overview

Rope fish are also sold as reed fish, snake fish, African rope fish, and by their Latin name Erpetoichthys calabaricus. They belong to the Polypteridae family, the same group as bichirs. They live in slow, reedy rivers, estuaries and swamps along the West African coast, from the Ouémé River in Benin to the Sanaga River in Cameroon (including Nigeria).

How long do rope fish live?

Keepers commonly report 15-20 years in captivity, which is far longer than most aquarium fish. Treat a rope fish as a long-term commitment. Young fish usually cost around $10-$20 and adults more, but the real cost is the tank and the years of upkeep.

How do rope fish behave?

Rope fish are mostly nocturnal, hunting by smell at night. If you feed them in the daytime, many learn to come out and eat then too. They spend most of their time on the bottom or tucked into caves.

They have gills and a primitive lung (a divided swim bladder), so you will sometimes see one dart to the surface for a gulp of air. Occasional trips are normal. Frequent trips can point to low oxygen or poor water quality. They need access to the surface, so don’t fill the tank to the brim with a gap that blocks air access.

They aren’t aggressive toward tank mates. The only exception is smaller fish being eaten after being mistaken for food. The other thing to plan for is jumping, covered below.

What do rope fish look like?

Rope fish have a long, cylindrical body covered in diamond-shaped scales, usually olive-green to brown. That color helps them blend into dark areas.

Most aquarium specimens reach about 12-20 inches. FishBase gives a maximum of about 37 cm (15 in), while some retailers and keepers plan for up to 20 inches, so build the tank for the larger number.

The fins are reduced. The small pectoral fins sit right behind the head and are often yellowish. The dorsal fin is a row of small finlets that usually lie flat, and there are no true pelvic fins. The body does the swimming by bending in waves, like an eel. Rope fish can also wriggle over land for short distances, one more reason to keep the lid on.

How can you tell male and female rope fish apart?

It’s difficult. Males tend to have more dorsal finlets (about 12-14 versus 9-12 in females), but they are hard to count on a live fish. During breeding condition the male’s anal fin swells and thickens. Without those cues, most keepers can’t sex them reliably.

What tank setup do rope fish need?

Rope fish live in conditions similar to many tropical community fish, so setting up their tank isn’t difficult. They come from warm, slow-moving water with a roughly neutral pH, plenty of cover and some debris such as rocks and wood. Wild fish also tolerate low-oxygen water because of their air-breathing ability, and FishBase lists them in both fresh and brackish water.

What water parameters do rope fish need?

Keep the water at 72-82°F with a pH of about 6.0-7.5 and hardness of 5-19 dGH. Seriously Fish and FishBase put the pH ceiling at 7.5-8.0, and the older figure of 6.7-7.8 sits inside that range. Stability matters more than hitting a specific number, because rope fish handle sudden swings badly. Slightly brackish water is tolerated, but it isn’t needed and shouldn’t be introduced if any plants or tank mates can’t take it.

What substrate, decor and plants work?

Use fine sand so the fish can’t scratch themselves. Add rock caves and driftwood, because they’ll spend much of the day hiding. Rope fish don’t eat plants, so a planted tank works well. Java Fern, Amazon Swords and tall stem plants like water wisteria are all fine. Make sure caves and gaps are wide enough that the fish can’t get wedged in, and check that any pipe or decoration opening is either too small to enter or large enough to exit easily.

What filtration do rope fish need?

They’re predators that produce plenty of waste, so use a canister filter or another high-capacity filter and do regular water changes. You don’t need an air pump or strong flow, since they come from slow water. Keep filter intakes covered, as they can slip into small gaps.

Do rope fish jump out of tanks?

Yes, and it’s the most common way they’re lost. Use a tight-fitting lid, and seal gaps around filter tubing, heater cords and feeding holes. A rope fish can squeeze through a gap that looks far too narrow.

What size aquarium do rope fish need?

Plan on at least 50 gallons for one fish, and 75 gallons or more if you want it to be comfortable as an adult. Seriously Fish recommends a much larger tank for a full-grown adult (a base around 150 x 60 cm, roughly 140 gallons), so treat 50 gallons as a bare minimum. Choose a long tank with plenty of floor space rather than a tall one. Add roughly 15 gallons per extra rope fish.

What are the best rope fish tank mates?

Rope fish are peaceful, so you have plenty of options, with two rules. First, the tank mate must be too big to swallow. Second, it must not be aggressive or territorial.

Rope fish are predators and will eat anything that fits in the mouth, even though fish aren’t their main food in the wild. They can’t tell a tank mate from a snack, so tetras, danios, and harlequins will vanish.

Good rope fish tank mates include Angelfish, Bala Sharks, Clown Loaches, Dwarf Gouramis, Glass Catfish, Pictus Catfish, Plecostomus, Rainbow Sharks, Siamese Algae Eaters, and Yo-yo Loaches. Other keepers report success with large Synodontis catfish and other bichirs of similar size. Check the adult size of any fish before buying: a juvenile that fits in the rope fish’s mouth today may be safe in a year, but the rope fish will grow too.

Avoid aggressive cichlids (such as Convicts and Oscars), which will harass or injure a slow-moving rope fish. Also avoid shrimp and small snails, which get eaten.

Rope fish find food mostly by smell and are slow, so they can lose out to fast, greedy feeders. Watch that yours actually eats.

Can you keep rope fish together?

Yes. You can keep one alone or a small group. Some keepers find groups more active, but each extra fish needs around 15 more gallons and more cave space, so only do it if the tank is big enough.

What do rope fish eat?

Rope fish are carnivores. In the wild they eat crustaceans, insects and worms, and fish only occasionally. They are nocturnal feeders, but they learn your routine and will eat in the daytime.

Meaty frozen foods work best: bloodworms, brine shrimp, mysis shrimp, prawns, mussel and earthworms. Live foods encourage natural hunting but add a parasite risk if collected from the wild. Many rope fish refuse dry foods, though sinking carnivore pellets are worth a try, especially for young fish. A hungry rope fish will eat tank mates, so don’t skimp on food.

Feed after the lights go down or just before. A small portion daily, or a larger meal every other day, both work. Remove uneaten food within a few hours.

How do you keep rope fish healthy?

Rope fish are hardy, and a well set up tank that’s kept clean keeps them healthy. They don’t cope well with sudden changes, so do moderate weekly water changes, match the temperature of new water and test regularly.

What are the signs of illness?

Watch for loss of appetite, hiding all the time, lethargy, clamped or damaged fins, cloudy eyes, wounds, or rapid breathing and frequent gulping at the surface. Ich shows as small white spots. Because of the fish’s long body, even small injuries from sharp decor or from escape attempts can become infected.

Can you treat rope fish with salt and medication?

Treat carefully. Rope fish and their bichir relatives are generally considered sensitive to some medications, so start with a lower dose than the label calls for and watch closely, or ask an aquarium vet or an experienced fish store. If you use aquarium salt, raise it slowly and in small steps. Don’t dose heavy amounts of salt in a freshwater tank.

Can you breed rope fish?

Not in a home aquarium, realistically. Seriously Fish lists breeding as unrecorded in aquaria, and commercial supply comes from wild-caught or farm-raised stock. Spawnings you may read about usually involve hormone induction, which isn’t something a home keeper can do. Expect to enjoy them as individual pets rather than a breeding project.

Are rope fish right for your aquarium?

They suit you if you have a large, long tank with a secure lid, peaceful mid-sized tank mates and a willingness to feed meaty food. They don’t suit a tank with small fish, shrimp, or aggressive cichlids.

Rope fish are slow, odd and interesting to watch as they slither around the bottom of the tank at night.

Frequently Asked Questions

What fish can live with ropefish?

Large, peaceful fish that can’t fit in the ropefish’s mouth. Angelfish, bala sharks, clown loaches, large gouramis and Synodontis catfish are common choices. Avoid tetras, rasboras, danios, shrimp and aggressive cichlids.

Are rope fish good community fish?

Yes, in a community of large, peaceful fish. Rope fish are calm and slow-moving, but they eat anything that fits in their mouth and can lose out to fast, greedy feeders, so small fish and shrimp don’t work as tank mates.

Can rope fish live with angelfish?

Yes, angelfish are a common rope fish tank mate. They are too big to swallow and peaceful enough not to bully a slow, nocturnal feeder. Keep the tank at least 50 gallons with a long footprint, and check that the rope fish is getting its share of food.

What do ropefish eat?

Rope fish are carnivores that eat meaty foods such as bloodworms, brine shrimp, mysis shrimp, prawns, mussel and earthworms. Many refuse dry food, though sinking carnivore pellets are worth a try, especially for young fish. Feed after the lights go down or just before.

Are ropefish aggressive?

No. They are calm and slow-moving, and they rarely bother fish they can’t swallow. The risk is predation on small fish, not fighting.

What size tank does a ropefish need?

At least 50 gallons for one fish, and 75 gallons or more for comfort. A long tank is better than a tall one. Add about 15 gallons for each extra ropefish.

What attracted you to keeping Rope Fish? Let us know in the comments section below…