Keeping Dinosaur Eels (Bichirs) In Tropical Freshwater Fish Tanks or Aquariums

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Dinosaur eel

The dinosaur eel is the common name for the Grey Bichir, Polypterus Senegalus, though it is a fish and not an eel. There are more than a dozen species of this fish but the Grey Bichir or Senegalus Bichir is the most common and is popular among aquarists. This Bichir is covered in dark grey horizontal bands that become paler as the fish grows. Some Bichirs can reach over three feet in length, although most species, including the Senegalus Bichir, grow to around one foot.

Natural habitat

In their native habitat they can be found in lakes, rivers, floodplains and swamps in Africa, especially the Congo River and Nile. They are capable of surviving in waters with low oxygen content and can move in search of food or to find other wet areas in their home dries in time of drought.

Characteristic features

The misnomer of dinosaur eel (hereafter referred to as Bichir) comes from the prehistoric appearance of this elongated fish. Its snake-shaped body is covered by thick, bone-like scales made of an enamel-like substance called ganoine, which resembles the now extinct earliest ray-finned fishes. It has a distinctive series of up to 18 dorsal finlets, each one with a sharp spine, which are erected when it is agitated. The fleshly pectoral fins, which control the slow movement of the fish, are attached behind and below the gill openings. It is also able to travel over land using its strong pelvic fins. Bichirs can also breathe air via a lung-like modification to their swim bladder. Other characteristics include a pair of blowholes, a long lower jaw and external nostrils which protrude from the nose to enable the Bichir to hunt by smell since its eyesight is poor. Females tend to be larger than males, while adult males have thicker dorsal spines and broader anal fins.

Diet

Bichirs are predatory and essentially carnivorous and will attack and feed on small fish that are easy to swallow as well as slow-moving fish. They will also eat insects, crustaceans and frogs. Since they are nocturnal they will feed mainly at night.

Breeding

After a series of energetic twisting movements, the male Bichir fertilizes the eggs by enveloping the female’s genital opening with his anal and caudal fin. He then scatters the eggs using thrashing movements of his tail. It is difficult, however, to get Bichirs to breed in captivity. Some aquarists have noted that even if a male and female are present, the male is often unresponsive and will not fertilize the eggs the female releases.

Aquarium size

Due to the length Bichirs grow and their need to breathe air, it is important they are housed in long tank aquariums that are not too deep, possibly even a fish tank table. Aim for an aquarium that is at least three times the adult size of the Bichir you have or plan to purchase. Choose fish tank aquariums that are no more than eighteen inches deep and do not fill completely with water. This is important as Bichirs need to be able to breathe from the air and therefore have to be able to swim quickly to the surface and back to the bottom where they dwell.

Being able to use oxygen from the air enables Bichirs to survive out of water for several hours. Given this and the fact that they have the instinct to move out of one place in search of food in another, it is recommended to have a tight-fitting lid on your aquarium!

Aquarium decor

A thin layer of soft sand or gravel is fine as substrate. Bichirs also like hiding places, especially as they prefer to stay out of the light during the day. So it is much more enjoyable for them to have robust plants, rocks and tunnels which allow them to display more natural behaviours. Plants attached to wood work best as Bichirs tend to displace plants rooted in the substrate because of their size and when searching for food.

Water conditions

As they are tropical freshwater fish, Bichirs require a temperature of 75-85 F. They like a pH of 7 or slightly below and prefer water that is a little hard. Of course, it is important to perform frequent water changes to ensure the quality of water is good in your tropical freshwater aquariums.

Aquarium lighting

Bichirs are nocturnal so they will be typically lethargic during the day and active at night. Rather than switching the aquarium lights off complete, provide the semblance of a natural nightfall by installing a blue moonlight bulb so you too can experience some action from your Bichir!

Feeding

Being carnivorous, Bichirs love to be fed baitfish, mussels, shrimps and bloodworms. They will also readily accept frozen foods. Some aquarists have tried to encourage them to take dry foods by only supplying them until their hunger overcomes them, and have found they can adapt OK. However, I would mention that this is not their natural diet.

Tank mates

Given the large size of Bichirs and their predatory nature, it is extremely important to match them with suitable tank mates. Do not keep them with fish smaller than three inches which can provide a ready meal! It is better to match Bichirs with bigger fish as they will not bother as much with fish they cannot swallow. Siamese Tigerfish, Angelfish, large Barbs, Cichlids and Knifefish are possible tank mates. It has been observed that suckermouth Catfish tend to suck on the skin of Bichirs which irritates them and so it is not advised to keep both types of bottom-dwelling fish. Also avoid matching them with overly aggressive species. In a very large fish tank it will be possible to keep several Bichirs together, provided they are around the same size. They should generally tolerate each other, apart from fighting over the food!

To keep or not to keep?

Bichirs are interesting specimen fish but do be aware of all the issues involved in keeping them, especially the size of the tank and the other tropical freshwater fish you have or plan to have. Bichirs also cost more to keep than other fish, though they are a very hardy breed. Keeping Bichirs in a suitable environment requires careful planning!