Rope Fish Care: Tank Size, Tank Mates, and the Escape Problem

Quick answer: The rope fish (Erpetoichthys calabaricus), also called the reedfish, is a peaceful, prehistoric-looking freshwater fish that swims like a snake and is genuinely easy to care for. But it comes with three big catches most buyers miss. It is a world-class escape artist that needs a completely sealed lid, it is a slow, near-sighted predator that will eat any fish or shrimp small enough to swallow, and it grows to around 15 inches and lives 15 to 20 years, so it needs a large, long tank and a serious long-term commitment. Get those right, give it soft sand, hiding spots, gentle flow, and meaty foods fed after dark, and it is one of the most rewarding oddball fish you can keep.

Rope fish at a glance

The escape problem: seal every gap

If you take one thing from this guide, make it this. Rope fish are escape artists, and the most common way people lose them is finding them dried out on the floor. They are slim, strong, and endlessly curious, and they will push through any gap they can find, including the small cutouts around filters and heaters.

Two things make this worse. Rope fish can breathe air, and they can survive out of water for a while as long as they stay moist, which is exactly why an escaped one can slither a surprising distance before it is in trouble. So the answer is not just a lid, but a fully sealed one. Cover the whole top, and block every opening around cords, filters, and pipes with mesh or foam. At the same time, leave a small air gap between the water and the lid, because rope fish come to the surface to gulp air and can actually drown if they cannot reach it. A sealed lid with a pocket of air above the water is the setup you want.

What rope fish actually are

Despite looking like an eel or a snake, the rope fish is neither. It is a bony fish, the only member of its genus, and a close relative of the bichirs. Its family is ancient, with relatives dating back over 200 million years, which makes it a genuine living fossil. It has a long, ropey body, tiny fins set far back, and both gills and a lung-like organ that lets it breathe air, one reason it is so hardy in low-oxygen water. It is native to slow, vegetated fresh and brackish waters across West and Central Africa, and it is nocturnal, doing most of its exploring after dark.

Setting up the tank

Rope fish are easy to please once the tank suits their size and habits.

• A long tank with floor space. This is a bottom-dwelling fish that reaches 15 inches, so floor space matters far more than height. Aim for a long tank of at least 45 to 55 gallons, and bigger for a group.
• Soft sand substrate. Rope fish forage along the bottom and will even bury themselves when startled, so use soft sand rather than sharp gravel that can scratch them.
• Plenty of hides. Driftwood, smooth rock caves, and dense planting give them the shady retreats they love. Our fish tank decorations guide covers safe caves and wood.
• Tall, hardy plants and dim light. Heavy planting with tough species and subdued lighting suits their nocturnal nature. Our low light aquarium plants guide has good options.
• Gentle filtration. They come from still and slow water, so filter efficiently but keep the current soft.
• The sealed lid, as above. Non-negotiable.

Unlike the small community fish in our 20 gallon fish tank guide, a rope fish is not a nano pet, so do not try to squeeze one into a small tank.

Water parameters

Keep the temperature between 75 and 82 F, the pH between 6.5 and 7.5, and the water soft to moderately hard. Rope fish are hardy, but they have two sensitivities worth respecting: they do not handle pH swings well, and they dislike rising nitrates. So keep the water stable and do regular partial water changes to keep nitrate low. Steady beats perfect with this fish.

Diet and feeding

Rope fish are carnivores, and feeding them is the second thing people get wrong. They are slow, nocturnal hunters with poor eyesight that find food mostly by smell, which means in a tank of fast, greedy fish they get out-competed and can slowly starve.

Feed a varied meaty diet of frozen and live foods such as bloodworms, brine shrimp, chopped prawns, mussel, and earthworms. Many will eventually take sinking carnivore pellets, but a newly imported rope fish often ignores dry food at first. The key is to make sure the food actually reaches them: feed after lights-out when they are active, and target-feed near them if quicker tankmates are stealing everything first.

Temperament and tank mates

Rope fish are peaceful and will ignore most tankmates. The catch is that they are still predators, and anything small enough to fit in their mouth is food, not a friend. That rules out small fish and shrimp entirely.

Good tank mates are peaceful fish too big to be eaten and not aggressive enough to bully or out-eat them: angelfish, larger gouramis, congo tetras and other bigger peaceful tetras, Synodontis catfish, and peaceful medium cichlids like severums. If you already keep angelfish, they make a natural match.

Avoid these:

• Small fish, dwarf shrimp, and snails, which will be eaten.
• Aggressive or fin-nipping fish, which will harass them.
• Very fast, greedy feeders that will strip the food before a slow rope fish finds it.

Keeping rope fish together

Rope fish are sociable with their own kind and often do best in a small group, so keeping two or three together is a lovely way to see natural behavior, with them piling into the same cave and slithering around together. A single one will still be perfectly content, so a group is a nice option rather than a requirement.

Breeding rope fish

Set your expectations low here. Rope fish are very rarely bred in home aquariums. Nearly all the ones for sale are wild-caught, captive spawning has only happened a handful of times, and there is no reliable home method. A few keepers have triggered spawning by simulating the rainy season with cooler, softer water, but raising the young is a specialist challenge. Enjoy this one as a display fish, not a breeding project. Because they are wild-caught, it is also worth knowing the species is considered near-threatened, so buy healthy stock and give it a good long life.

Common rope fish mistakes to avoid

• An unsealed lid. The single most fatal mistake. Seal the whole top and block every gap.
• No air gap. They breathe air, so leave a space above the water so they can reach the surface.
• Keeping them with small fish or shrimp. These become snacks.
• Letting them starve. Slow and near-sighted, they lose out to fast feeders, so feed after dark and target-feed.
• Sharp gravel. Use soft sand for a bottom-dwelling, burrowing fish.
• Too small a tank. A 15-inch fish that lives 20 years needs real space, not a starter tank.

FAQ

Do rope fish need a lid?

Yes, absolutely, and it must be a fully sealed one. Rope fish are notorious escape artists that squeeze through the smallest gaps, so cover the whole top and block every opening. Leave a small air gap above the water, since they breathe air at the surface.

How big do rope fish get?

Around 15 inches is typical in an aquarium, and some reach close to 20. They are long, bottom-dwelling fish, so plan for floor space, not just volume.

What size tank does a rope fish need?

A long tank of at least 45 to 55 gallons for one, and larger for a group. Floor space matters more than height for this species.

Can rope fish live with other fish?

Yes, with the right ones. They are peaceful toward fish too big to eat, such as angelfish, larger gouramis, and Synodontis catfish. But they will eat any fish or shrimp small enough to swallow, so avoid nano fish and shrimp.

What do rope fish eat?

They are carnivores that prefer meaty frozen and live foods like bloodworms, prawns, and earthworms. Feed them after dark, since they are slow, near-sighted, nocturnal hunters that can be out-competed by faster fish.

How long do rope fish live?

Commonly 15 to 20 years with good care, which makes them a long-term commitment. Be ready to house one for that long before you buy.