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Issue: August 2007

Understanding the Reedfish

Author: Phil Purser


Photographer: Joe Gallo
One of the most bizarre fish in the hobby, the reedfish Erpetoichthys calabaricus commands the attention of many aquarium hobbyists—but to keep it properly requires some experience and know-how.

“I want that one,” I said, mashing my index finger against the glass wall of the pet shop’s display aquarium. My father’s gaze trailed my pointing finger and came to rest on an elongate purplish creature tooling about a cluster of artificial plants. Looking more like an aquatic snake or baby sea-serpent than an aquarium fish, the unusual animal got the typical response from my father.

“Um…” he replied, slowly scratching his chin, “why don’t we get some nice guppies? Or zebra danios? You know, your school is getting pretty small, and they like to have plenty of buddies. Let’s get some more zebra danios.” As my father led me away from the snake-like creature, my high hopes of owning the most unusual fish I’d ever seen quickly faded into little more than a wistful memory. Though I went home that day with a bag full of zebra danios, I knew in the back of my mind that one day I’d be taking home one of those purple-hued snakefish that I’d fallen in love with that day.

Well, nearly three decades have passed between that day and this, and in that time I’ve owned more than a few of those mysterious serpentine fish. Known to the scientific community as Erpetoichthys calabaricus, the fish I refer to is the reedfish. Frequently appearing in the pet trade as the “ropefish” (owing to its similarity in appearance to a strand of braided rope), the reedfish may also be sold under the Latin moniker Calamoichthys calabaricus. Whatever name it goes under, this fish is truly one of the most bizarre community tropicals that the average hobbyist could ever own. The reedfish’s curious appearance, healthy appetite, and exceptionally hardy constitution make it a fish that is aesthetically pleasing, easily cared for, and long-lived. Of course, there are a few things that the interested hobbyist should know about these fish before dropping one into his or her tank.

Natural History

Discovered and formally described by J. A. Smith in 1865, the reedfish is one of only 11 species known to exist in the family Polypteridae. The reedfish is an ancient creature; fossil records show these fish as swimming the earth’s waters over 70 million years ago. Once found throughout all of central and northern Africa, the reedfish is now confined to the slow-moving basins and sluggish backwaters of the Niger and Congo rivers and their tributaries in west-central Africa.

Like all other members of the Polypteridae family, the reedfish has a rudimentary lung-like structure attached to its intestinal tract. The reedfish uses this organ to extract oxygen directly from the atmosphere. In times of drought, or when the water conditions are exceptionally poor, these fish survive by rising from the depths of their pool, gulping a lungful of air from the atmosphere, and diving back to safety while the atmospheric oxygen absorbs into their bloodstream. While this ability to gulp air may appear to be an excellent tool for survival, it has a considerable downside. In order to survive, reedfish must rise to the surface periodically to gulp air, as their gills are incapable of collecting sufficient oxygen from the water, no matter how well oxygenated the water is. This means that at intervals throughout the day, these fish must surface to breathe, thereby placing themselves at high risk from predators both on land and in the water. A host of snakes, birds, and predatory fish in central Africa are quick to snag a surfacing reedfish whenever the opportunity presents itself.

Fortunately the reedfish has more than one survival trick up its sleeve. Not only does its purplish to brown dorsal coloration help keep the reedfish hidden from sight, but its cryptic lifestyle makes it a rare meal to all but the most efficient predators. As its common name suggests, the reedfish lives among the reeds, roots, and vegetative cover of the riverine or swampy shallows. When its snake-like body is lying motionlessly entwined in a cluster of gnarled and twisted roots, the dark-colored fish can quite literally disappear in plain sight when viewed from above. Similarly, the pale yellow to tan of the reedfish’s ventral surface makes the fish hard to see when viewed from beneath by a lurking predator.

Even in the rare instance when this camouflage strategy fails, the reedfish has one more tactic for survival. The substrate of its native waters consists of tiny pebbles, decaying vegetative matter, and loose, fine-grained sands. When danger is afoot, the wily reedfish will sink its flat, shovel-like head beneath the sand and push vigorously forward. In a matter of seconds, the entire fish has buried itself beneath the sandy riverbed, thereby escaping virtually all sight-reliant predators.

Of course these tools of survival function not only to hide the reedfish from its predators, but they serve also to conceal the stealthy fish from its intended prey items. Unsuspecting fish, crustaceans, and insect larvae that venture too close to a hiding reedfish will very likely end up on the menu, for while it is fluid and graceful in its normal snake-like undulations, a hungry reedfish can move with alarming speed when it goes in for the kill. These fish also come equipped with peg-like teeth and powerful jaws, both of which function to crush and grind prey into digestible bits. Few fish or inverts that have become the target of a hungry reedfish ever escape to live another day.

Reedfish in the Aquarium

As you might imagine, reedfish are and have always been popular aquarium captives among those hobbyists who have a taste for the bizarre. Looking more like snakes than fish, these animals have elongate bodies that are heavily clad in overlapping, shingle-like scales. The fan-like caudal fin and the rhythmic undulations of the body allow the reedfish to move easily and gracefully along through even the thickest of underwater vegetation. The broad, strong pectoral fins also allow for excellent maneuverability in tight places or when sneaking up on prey. This unique, sea serpent-like body morphology has made the reedfish especially popular among children and young hobbyists.

Housing a reedfish in captivity is only slightly different than housing any other tropical fish. Because adult reedfish may grow 3 feet long, they must be housed in an aquarium that is large enough to accommodate an animal of such proportions. Therefore I recommend that no tank smaller than 50 gallons even be considered to house a reedfish throughout the duration of its lifetime. Because these fish are so long, the floor space of the aquarium is more important than the absolute volume of the tank. For example, a tank that is taller than it is wide or long is of little value to the reedfish, as such a tank affords the fish little room to stretch out and swim. A tank that is much longer and wider than it is tall, however, is just what your reedfish needs to swim and tool about the horizontal lengths of its domain.

Preventing Escape

Once you find a tank of the proper dimensions to house your reedfish, you must then tackle the daunting problem of aquarium security. When it comes to security, the reedfish are no ordinary tropical species. Reedfish are absolute masters of escape, and even a large individual can wriggle through a small gap or hole in the lid of your aquarium. Adult reedfish are also surprisingly strong, able to pry up and lift unsecured plastic aquarium lids in order to escape.

Thwart all escape attempts by shoring up any and all gaps, holes, or cracks in the lid of your aquarium. Make sure that all return stems, hoses, intake valves, and hang-on style filters leave no more than ¼-inch gap between themselves and the lid of your aquarium. If a large gap must remain in your lid (such as is necessary for a trickle filter’s return flow of water), you should cement (via aquarium-safe silicon gel) a section of fine mesh nylon or rubberized screed into the lid so that your filter’s return water may flow uninhibited into the tank, but no wandering reedfish can slither out of the tank. A weighted or locking lid is also in order, as an adult reedfish may learn that lifting the lid of the tank, even slightly, allows access to the world beyond the aquarium. Thwart this avenue of escape by employing heavy glass lids on your aquarium, rather than those flimsy black plastic varieties, which are lightweight and do not provide any real security when it comes to reedfish.

A final matter of security is to shore up all filter apparatuses. Reedfish are curious and exploratory by nature, thus an open-ended filter intake stem might be too appealing for the fish to pass up. Should it slither into the intake stem it will almost certainly be unable to get out and will die inside your filter. In the best case, your reedfish will perish, and in the worst case your reedfish will perish and your filter motor may burn up and lead to minor flooding of your carpet (depending on what style of filter you have). In either event it makes for a bad day for the hobbyist. Prevent such maladies by securing all filter apparatuses before introducing a reedfish into your system.

Decorating the Aquarium

Most experts agree that a naturalistic approach the best way to go about decorating a reedfish’s aquarium. Reedfish have lived and thrived in the swamps of central Africa for over 70 million years for a reason: they are highly adapted to life in slow moving, heavily planted areas. While the resilient reedfish can survive in less adequate environs (plain, barren, or sparsely furnished tanks), the wise hobbyist will do his or her best to closely simulate the natural habitat of the reedfish.

Start by placing a 2- to 3-inch-deep layer of fine grained aquarium sand in the bottom of the tank. This sand may be mixed with small aquarium pebbles if desired, but for the long-term health and mental well-being of the reedfish, a layer of pure sand is highly recommended. Not only will your reedfish occasionally burrow into this loose substrate, but, being a sloppy eater, it may also ingest minute quantities of sand with its meals. Should the reedfish be housed upon pebbles, an ingested stone would likely prove much harder for the reedfish to pass than a small amount of sand.

Pre-washing the sand before putting it into your aquarium will remove all but the heaviest particles and will reduce the cloudiness of your aquarium should the sand be stirred up. Frequent changes of your filter’s particulate filtering media will be necessary for the first week or so after switching to a sandy substrate.

Once your sand is in place, you’ll need to plant the aquarium heavily. By “heavily,” I mean that there should be at least one living plant per every 2 to 3 square inches of the aquarium’s floor space, though not all the plants have to be rooted in the bottom, nor must they be evenly distributed throughout the tank. In the wild, reedfish frequently hunt along the edges of dense vegetation, and they often venture out into open water to snag a fish or a crustacean. Replicate this in your aquarium by densely planting one portion of the tank while leaving other areas only sparsely planted. This formation will give your reedfish plenty of “open water” in which to swim and hunt, while at the same time granting it all the security and cover it needs in the heavily planted regions.

Some aquarium plants of choice in the reedfish aquarium include Java fern, crystalwort, corkscrew Vallisneria, Amazon sword, and Aponogeton ulvaceus. Top-growing plants such as water lettuce and water hyacinth also work well, but these varieties should not be used in excess, as they must not be allowed to completely cover the water’s surface. The use of sunken driftwood is also highly recommended, as are acrylic or ceramic hides, shelters, caves, and other commercially manufactured aquarium decorations that are large enough for the reedfish to conceal itself inside.

Because reedfish are primarily nocturnal, they have little tolerance for excessively bright lights, so lighting should not exceed that which is necessary to stimulate plant growth. Daily lighting cycles of 8 to 10 hours are best, with nights (or unlit periods in the tank) lasting from 10 to 12 hours. Remember that your reedfish may seek retreat from the bright lights during the day, so don’t expect it to be too active. Reedfish can, however, be trained to be more active during the daytime by the scheduling of your feedings. By feeding your reedfish only at times when the aquarium lights are on you’ll be able to glean a higher degree of visibility and enjoyment from your hunting reedfish.

A Need for Oxygen

A final consideration for housing your reedfish is the matter of oxygen. In the wild, reedfish absolutely must surface every so often to gulp air directly from the atmosphere. In captivity, you must provide this air-gulping venue to your reedfish or it will soon die. Fortunately, this is easily accomplished by drawing a line on the outside of your tank with a magic marker. Draw the line–call it a lifeline, if you will–about an inch down from the top of the aquarium, and never allow the water level inside the tank to rise above this line. By leaving a one-inch gap between the water level and the top of the tank, you’ll ensure that your reedfish always has ample access to atmospheric oxygen.

Water Quality

Now that all the physical aspects of your reedfish’s aquarium are out of the way, we move on to the matter of water quality. Reedfish are very hardy, stalwart animals that are highly resistant to water-born diseases and parasites. That is not to say, however, that the hobbyist can afford to be lax when it comes to water quality. Being native to the tropical climes of equatorial Africa, the reedfish requires temperatures ranging from 73° to 82°F, with pH of 6.5 to 7.0. While reedfish are resilient to lower pH than some other tropical species, they are quite sensitive to radical changes in pH. Sudden pH swings of more than .1 or .2 can highly stress a reedfish, and fluctuations of much more than this can prove fatal. Warning signs of improper pH are paleness and pallor in the reedfish’s scales, eyes, and finnage.

Ammonia and nitrites/nitrates can also be problematic in the reedfish aquarium. Lax husbandry practices can very quickly rob a reedfish of its life when ammonia levels rise above 5 to 10 ppm. Warning signs of high levels of ammonia include short, jerky motions on the part of the reedfish, as well as very frequent air-gulping trips to the surface. Conduct regular water changes every week of 20 percent or more by siphoning the sand/gravel substrate, making sure to remove as much debris and biological refuse as possible from the water column. Premium filtration, obviously, is also a must in the reedfish aquarium. I personally recommend a mixture of undergravel filters and powerheads (angled upward toward the top of the water column), canister filters, and a trickle filter or two attached to back of the tank. More or less filtration may be necessary depending on the size of the tank, the size of the reedfish, and the number of any other community tropicals housed in the aquarium.

Feeding

The reedfish is largely an indiscriminate eater, consuming virtually every living thing placed before it. Newly arrived captives will eagerly dine on live freshwater shrimp, crickets, worms, insect larvae, and minced bits of fish. Feeder minnows and tiny guppies are also taken with relish. Older captive individuals may be weaned onto pellet foods and tablets, though these items should be soaked in a small dish of water for at least 5 to 10 minutes before offering them.

Reedfish have the tendency to swallow their prey items whole or in large chunks. Hard, rough-edged pellets and tablets can, and often do, induce choking when your fish eats them immediately after you drop them into the tank. Bear in mind also that multi-segmented prey items, such as worms, insects, and whole shrimp, will very likely leave behind body-bits (legs, antennae, body segments, etc.) to pollute the water. Feeding such prey items to your reedfish absolutely necessitates more frequent water changes on your part. Organisms that your reedfish can swallow whole (i.e., minnow, guppies, tiny snails) will leave behind far less biological debris when eaten, thus your aquarium maintenance schedule need not be accelerated. Feed young and growing reedfish small meals twice daily, but feed adult specimens one larger meal only once every two days, or a single smaller meal once per day.

Choosing Tankmates

A final consideration when housing reedfish is the matter of tankmates. Perhaps my father knew so long ago that while the zebra danios of my tank would never eat their aquatic companions, the reedfish I was eyeballing just might make a midnight snack out of any one of its fellow captives. And he would have been right.

The bottom line is that reedfish are predators, and anything that is small enough to fit into their jaws is on the menu. Guppies, mollies, platies, neons, small tetras, rasboras, and just about any other fish or invertebrate that is the same width or narrower than the width of the reedfish’s head is at risk of being eaten. Similarly, any fish that shares the lower levels of the aquarium with the reedfish is likely to come under the knife in the dark hours of the night. Loaches, small catfish, and bottom-dwelling invertebrates or amphibians (African clawed frogs, tadpoles, newts, etc.) are all in danger when a reedfish is on the prowl.

Perhaps the best tankmates for the reedfish are the barbs. Strong, fast swimming, mid-level fish, the barbs typically grow large enough that a reedfish will not consider eating them. Tinfoil barbs, bala sharks, angelfish, large gouramis, Australian rainbow fish, etc. are all good choices. Larger catfish such as channel cats and small blue catfish are also acceptable, as are top-level swimmers such as African butterflyfish and the South American hatchetfishes. If given ample hiding areas away from the reedfish, most species of knifefish will also fare well when housed with a reedfish.

Very large aquaria may successfully maintain multiple reedfish, though plenty of hiding places and territories must be afforded to each specimen to ensure a peaceful coexistence. Bear in mind also that the same fishes that are acceptable tankmates when the reedfish is small may become dinner when the reedfish goes larger. Size appropriateness is the main factor when considering tankmates for the African reedfish.

Father Knows Best

In retrospect, I guess dad did the right thing in not buying me a reedfish that Sunday afternoon in the pet shop. I’d have gotten it home, put it in my tank, and watched my smaller fish disappear one by one. Then I’d have cried when one day I found the reedfish dried up and dead on my bedroom floor, for my childhood aquarium had more holes, cracks, and gaps in the lid than I could have counted on both hands. Reedfish are fun, curious, and bizarre fish, but they are definitely for the more experienced hobbyists among us. Any children wishing to own one should only be allowed to do so under the careful guidance of an adult hobbyist.

By shoring up your tank, adding a healthy stand of live plants, optimizing your filtration, and stocking up on appropriate foods before acquiring a reedfish, you’ll go a long way in ensuring that you and your new pet “sea serpent” have as long and as fruitful a relationship as possible.

 
 
 

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