Ask the WWM Crew
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Truly ancient fishes that make great and interesting aquarium subjects the air-breathing oddities we call Bichirs and the Ropefish are easy to accommodate and care for; given that you pick out healthy specimens and keep your tank covered!
Bichirs (sounds just like the motorcycle kind) and the Ropefish are hardy predators that epitomize toughness and disease resistance; asking only adequate bottom space, decent water quality and occasional meaty meals.
Let's review the pertinent husbandry of this "many-finned" (the meaning of their family name Polypteridae) fishes, and relate the principals of how to select worthy specimens.
Classification: Taxonomy, Relation With Other Groups
Take a look at these fishes, what do they look like to you? More like water breathing reptiles than fishes in many respects, with their lobed fins, hard, rhomboid scales, terminal mouths and bottom-crawling locomotion. Early investigators lumped the family Polypteridae ("Poe-lip-tur-id-ee") for many years with the even more ancient lungfishes and coelacanth; current theories place them as survivors of an early ray-finned true bony fish group.
As mentioned the family moniker is for the "many-fins" (poly, pter) making up the retractable dorsal. Each of these 5-18 finlets (per species) is composed of a hard spine and one or more soft rays. An interesting parallel with tetrapods (amphibians, reptiles, birds and mammals) is the presence and use of "lungs" in Polypterids. Their "gas-bladder" does double-duty as a respiratory organ; it's bi-lobed, connected to the throat via a closeable duct, and ventral to the esophagus (as opposed to most fishes where it's dorsal). Hmmmm. Yes, these fishes will drown if prevented from reaching the surface to augment oxygen intake. More about this below.
Species of Use/Availability to Aquarists:
There are two genera, at least ten species and a bewildering number of subspecies of Polypterids recognized by various authors. Thankfully the habits and care for all are closely similar.
The other Polypterid genus, the torpedo-shaped Polypterus have pelvic fins. Polypterus includes at least nine species, a handful of which make their periodic way into the trade.
Other Polypterus species are exceeding more rare in captivity due to geographic/infrastructure limitations, or achieving too-large size.
All Polypterids are freshwater, and confined to tropical Africa. There is fossil evidence of Polypterids in South America in existence before it's separation with Africa.
In the wild one Bichir species approaches 90 cm. in length; yes, some three feet! Most species max. out at 30 cm., or about a foot in aquariums, with a few, including the reed or rope fish getting to a couple of feet.
Selection: General to Specific
Things to look for in picking out Polypterids are actually limited to two concerns; these fishes arrive in one of two "categories"; tough and ready to go, or damaged and gone.
1) Time on hand is utmost critical. All Reedfish and Bichirs are wild-collected, many via native plant poisons, and these tend to have very poor survival. Others have had a rough time of being hand or trap collected, starving in anticipation of transit, and long shipping in crowded, contaminated water conditions. The only way practical to get beyond these induced losses is to wait out a period of time; most all that are going to die will do so within a week or two of arrival. Hold on deposit, or insure that yours have been on hand at least this long before purchasing.
For wholesale/importer types, please do your bit by running new arrivals through a copper/formalin bath and/or a regimen of DTHP (Dylox, Dipterex, Neguvon...) over a period of a week to knock off flukes and protozoans before sending your stock on.
2) Red marks, bruising, sores are generally obvious on damaged, otherwise new arrivals and doomed specimens; especially around the "nostrils" and fin origins. Don't buy these fish, or any others in their system.
3) Netting and moving in general. Just a note to be aware that these fishes, oh so slow underwater, are squirmy, slimy, spiny and aerial escape artists! Either utilize your net to direct them into a large bag underwater, or if you feel you must lift yours into the air, utilize a VERY LARGE SOFT NET... and keep your hands away! The dorsal finlets on Polypterids are sharp, and on large specimens, formidable weapons... and they know it. You've been informed/warned.
Polypterids are decidedly nocturnal and otherwise secretive in their habits, appreciating subdued lighting, plenty of non-sharp decor and vegetation. Though other sources encourage the use of fine sand I don't. Bare tanks or dull aquarium gravels work just fine, and are easier to keep clean.
These fishes are tolerant of a wide range of conditions, but prefer neutral to slightly acidic (7-6.5) pH, tropical (75-mid eighties F.) water of up to medium hardness. By and large all potable waters will work, and I have yet to see specimens lost due to adverse tap quality except in situations where aquarists were fooling with their water chemistry. My advice? Stick with regular, partial water changes (10-25 percent per week) to mediate aging water quality.
With such occasional diggers and using live plants, I reject using undergravel filtration. Outside power (hand on or canister), and/or inside power filtration is advised without mechanical aerators ("bubblers") if you have a real aquarium (i.e. one with live plants) that is as under-crowded as it should be.
A not so deep tank of as large a capacity as practical, let's say a good four plus times the length of your specimen/s is a good start. Not too crowded, especially with other bottom dwellers or bite-size tank-mates. The shallow, flat aspect of a "standard" versus "show" style tank accommodates these fishes need for cruising space and proximity to surface air.
Again, a note re jumping, as in out; your lid must be complete and secure, maybe with a latch mechanism or weight on top. If the underside has sharp edges, or is hot from the lighting, do lower the water level to prevent cutting or burning your Polypterid.
So, you didn't listen and you find your Ropefish, Bichir on the floor as so much fish-jerky. Don't give up so quick! Even if stiff-ish, rinse that aquatic Houdini off with tank water and put it back in for a few hours. Quite often a "dried-up dead" jumper will reconstitute and return to the land of the living.
Wholesalers get away with purposely overcrowding these fishes as a practical matter, ala many African and Neo-tropical cichlids; you shouldn't do this. Bichirs are often agonistic toward their own species and will bite. Unless you have a HUGE (hundreds of gallons) system and are determined to make a try at spawning, keep them one to a tank. If undeterred by my warning, or a breeder wanna-be, purchase and introduce your Bichirs all at once, and keep your eyes open, net in hand, to separate them should things turn nasty. Reedfish are much more social, and best displayed in multiple numbers.
It's best to put these fishes in last or close to it, to allow for "seasoning" of the water and filtration; as well as to give other livestock (fishes, plants) an opportunity to get situated and a feel for the layout of the system.
A new Bichir or rope may be summarily floated and released as most freshwater livestock, with the lights off for the rest of the day. Pay attention the following morning that your new addition is well and gets something to eat.
Polypterids get along with most everyone that gets along with them with the exception of con- and near-specifics and mouth sized tank-mates. Slow, small fishes and invertebrates will be stalked and inhaled; and they are, as you might surmise, easily out-competed for food by faster, more aggressive tank-mates.
Reproduction, Sexual Differentiation:
Riehl and Baensch (1996) list structural and color differences for the Reedfish as follows; the male bears 12-14 bars on his olive caudal fin, versus 9 for the females' which are light ochre during spawning times.
Amongst Polypterus, males have slightly larger anal fins and females bigger heads. Males initiate spawning, the female laying a few hundred eggs near his hand-like anal fin. Young hatch out in about four days in tropical temperatures. A few species have been bred in captivity with young raised to maturity.
I'd like to mention the Polypterids curious use of pectoral fins, "walking" on the bottom by way of pulling on these lobed appendages. The tail fin and musculature is used only for periodic forays to the surface for a gulp of air and when the animal feels the need for a burst of speed.
Feeding/Foods/Nutrition: Types, Frequency, Amount, Wastes
All sorts of meaty foods, live and prepared are accepted by healthy individuals. Shrimp, worms (true and insect larvae like mealworms), crustaceans of all sorts, cut meat (beef heart, horse), frogs, newts, cut and small fishes and more are accepted. Be leery of offering monotonous diets as these fishes can get overly accustomed to nutrient-insufficient foodstuffs.
A feeding stick to direct items near the Polypterids, or sinking foods that won't be consumed by everyone else will assure your Polypterid is getting his/her grub.
Should yours go on a hunger strike, try a sizeable water change (25%) and offer a live earthworm, mealworm or such on a daily basis. I have yet to see a Bichir starve when offered these.
Polypterids do succumb to ich and other protozoans, but only after most other types of fish tank-mates have become infected and died. The group respond favorably to standard treatments for the same. There are a number of monogenetic trematodes (flukes) that infest their skin and gills, but they should be eliminated by your dealers far in advance of your acquisition.
One final disease comment. A small amount (a teaspoon or less) of non-iodized salt in concert with water changes often serves as a ready tonic in boosting Polypterid vitality.
Looking for an oddball, really neat, perhaps "species" tank specimen. Search no further. The Bichirs and Reedfish are great candidates. Once you secure healthy stock, place it in a large, decorated, planted tank, you will be in for a long term relationship. Just be sure to keep that top battened down!
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Baensch, Hans A. & Rudiger Riehl. 1993. Aquarium Atlas, v.2. BAENSCH, Germany. 1212pp.
Burgess, Warren E. Bichirs and rope fish. TFH 1/83.
Castro, Alfred D. 1995. Back again; The reemergence of an aquarium fish from the 60s (Bichirs). AFM 5/95.
Donovan, Paul. 1992. Beautiful Bichirs. FAMA 2/92.
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Lewis, Peter A. 1996. The Bichirs; Ancient fish with many fins. AFM 5/96.
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