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Mottled Bichir

(Polypterus weeksii)

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 Quick Care Facts

• Care Level: Moderate   • Temperament: Semi-aggressive   • Maximum Size: 22"
• Minimum Tank Size: 90 gallons   • Water Conditions: 76-84° F, KH 1-12, pH 6.5-7.5
• Diet: Carnivore   • Origin: West Africa   • Family: Polypteridae
• Species: Bichirs   • Aquarium Type: Large-Bottom-Dweller

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Species Information

Mottled Bichir native habitat, distribution, behavior & aquarium compatibility.

The Mottled Bichir (Polypterus weeksii) is a popular western African Bichir species known for its mild temperament and large head. While they are not aggressive towards other large fish species, their large head and corresponding mouth make them capable of eating surprising large fish. Tank mates should be carefully selected to make sure that they are large enough to not fit into the Mottled Bichirs mouth.

Within the aquarium trade the Mottled Bichir is often sold under a variety of names including: Weeks Bichir, Fat-headed Bichir, Fathead Bichir and of course Mottled Bichir. They exhibit a distinctive color pattern of dark grey bands over a light grey body, with a whitish under belly. In the wild the Mottled Bichir can be found living in the rivers, lakes, ponds and marshes of western Africa, where they forage amongst the substrate for small fish, worms, crustaceans and similar meaty foods.

They can grow upwards of 2 feet in length in the wild, but generally only grow to about 16 inches in the home aquarium. They are considered a semi-aggressive species since they will eat fish small enough to fit in their large mouths, but will not bother larger fish species. The majority of Mottled Bichirs available within the aquarium hobby are wild caught specimens; however, they do very well in the aquarium environment when provided proper water conditions and aquarium size.

Aquarium Care

How to successfully keep Mottled Bichir in the home aquarium.

An ideal aquarium setup for an adult Mottled Bichir will have a foot print of 6 x 2 feet or larger, a soft sandy substrate and a mixture of smooth rocks, plants and driftwood. Due to the shape of the Mottled Bichir and its swimming habits it is important to provide an aquarium with plenty of depth and length; however, the height of the aquarium can vary quite a bit as it is less important.

Being a nocturnal species, the Mottled Bichir will appreciate areas of the aquarium that are either not brightly lit or are shaded by vegetation or driftwood. Proper tank mates for the Mottled Bichir should be large enough to not be considered food (anything small enough to fit in their mouth), but not so aggressive that they will harass the Bichir.

Most larger semi-aggressive African Cichlids and New World Cichlids to quite well with Bichir, along with large Knife fish, other Bichir species, Synodontis and Datnoides species. Moderate to advanced hobbyists should have no trouble keeping Bichir in their home aquarium, as they are a very hardy species that has been successful in nature for millions of years.

Feeding & Nutrition

How to properly feed Mottled Bichir and provide a healthy diet.

The Mottled Bichir is a carnivorous species that will consume a variety of meaty foods both in the wild and the aquarium environment. Essentially the Mottled Bichir will see any other fish or invertebrate species in the aquarium that are small enough to fit in its mouth as food. However, in order to provide them the vitamins and minerals that they need to support a healthy immune system they should not be fed a diet solely of feeder fish.

A good diet for the Mottled Bichir will have a variety of meaty foods including: earthworms, prawns, mussels, raw shrimp and various types of feeder fish like silver sides and lance fish. Some Bichir have been known to accept commercial meaty pellets and wafers, but generally they do best with live or frozen foods. They should generally be fed 1 to 2 times per day an amount of food that they will consume within 5 minutes.

When first added to the aquarium, Bichir are more likely to feed with the aquarium lights off or dimmed as they are a nocturnal species. Being a nocturnal species with poor vision, the Mottled Bichir has developed an excellent sense of smell which they use to locate food in low lighting conditions. Feeding them with the aquarium lights off gives them an advantage over tank mates who use eyesight as a primary method of detecting food.

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