The Silver Arowana is a majestic predatory fish from the Amazon, growing up to one meter long, famous for its leaping ability and paternal mouthbrooding.
Overview
Osteoglossum bicirrhosum, or the Silver Arowana, is one of the most impressive freshwater fish that can be kept in a home aquarium. This ancient species belongs to the family Osteoglossidae (bonytongues) and is considered a true "living fossil," whose ancestors existed as far back as the Jurassic period. In the wild, the Silver Arowana inhabits the Amazon basin, the rivers of Guyana, and the Rupununi, favoring slow-moving and still waters with abundant bankside vegetation.
The Arowana reaches imposing dimensions — from 60 to 100 cm in length, making it one of the largest aquarium fish. Its elongated, laterally compressed body is covered in large silvery scales with a distinctive metallic sheen. The species name "bicirrhosum" translates as "two-barbeled" — two sensitive barbels on the lower jaw serve as sensory organs for detecting prey at the water's surface. The mouth is superior (upward-facing), adapted for hunting at the waterline.
The Silver Arowana is a legendary jumper. In the wild, it can leap 1–2 meters out of the water to snatch insects, small fish, and even birds and bats from overhanging branches. This ability dictates one of the key requirements for keeping this species — a secure, heavy, tightly fitting lid on the aquarium. With a lifespan of 10–15 years, the Arowana becomes a long-term and mesmerizing inhabitant of your tank.
Tank Requirements
Given the colossal size of the Silver Arowana, the minimum tank volume is 500 liters, although a capacity of 800–1000 liters is preferable for an adult specimen. The aquarium must be long and wide — at least 200 cm in length so the fish can turn freely. Tank height is less critical, but a lid is mandatory: the Arowana easily jumps out of the water, so the lid must be sturdy, heavy, and tightly sealed. Lightweight plastic covers can be knocked off by a single strike from this powerful fish.
Optimal water parameters: temperature 24–28°C, pH 6.0–7.5, general hardness (GH) 3–12 dGH. The Arowana requires a powerful filtration system — an external canister filter with a turnover rate of 3–4 times the tank volume per hour is the ideal choice. However, excessively strong current should be avoided, as Arowanas prefer calm waters in the wild.
Sand or fine gravel works well as substrate. Decorations should be minimal — large driftwood and rocks without sharp edges that could injure the fish during sudden movements. Plants are not essential, but floating species help create natural shade, which the Arowana appreciates.
Feeding and Diet
The Silver Arowana is a pronounced ambush predator that hunts near the water's surface. In nature, its diet includes insects, small fish, frogs, shrimp, and even small birds and bats that venture too close to the water. In the aquarium, high-protein foods should form the basis of the diet.
Recommended diet:
- Live and frozen fish (small-sized)
- Large shrimp and crayfish
- Crickets, grasshoppers, cockroaches, and other feeder insects
- Mussel and squid meat
- Specialized pellets for large predatory fish
Young Arowanas should be fed 2–3 times daily, while adults need feeding once a day or every other day. It is important not to overfeed and to vary the diet for complete nutrition. Avoid feeding prey that is too large, as it can damage the esophagus. Live feeder fish should be quarantined to prevent introducing parasites and infections.
Care and Maintenance
Osteoglossum bicirrhosum is a fairly hardy species, but its large size places serious demands on tank maintenance. Weekly water changes of 25–30% are necessary to maintain water quality and reduce nitrate levels, which accumulate quickly due to the predator's abundant feeding.
Powerful filtration is the key element of successful keeping. Regular cleaning of filter media and monitoring water parameters (temperature, pH, ammonia, nitrites, nitrates) should become routine practice. The Arowana is sensitive to sudden changes in water parameters, so all water changes should be performed gradually.
Pay special attention to the condition of the tank lid — this is critically important. The Arowana is one of the most powerful jumpers among aquarium fish, capable of dislodging an insufficiently secured cover. It is recommended to add extra weight to the lid or use special clamps. Any gaps and openings in the lid must be sealed.
Monitor the condition of the barbels — they can be damaged by impacts against tank walls or decorations. Damaged barbels usually regrow, but slowly. Lighting should be moderate, with the option to create shaded areas.
Compatibility
The Silver Arowana has a semi-predatory temperament (aggression level 3 out of 5). The main compatibility rule is simple: any fish that fits in the Arowana's mouth will be eaten. Given the size of its mouth, this excludes most small and medium-sized fish species.
Suitable tank mates should be large, able to hold their own, but not overly aggressive. Good options include:
- Large pleco catfish, such as the Sailfin Pleco
- Oscar and other large cichlids
- Bichirs — also ancient fish that coexist well with Arowanas
- Giant Gourami
- Large Pangasius catfish
Avoid keeping Arowanas with small fish, slow-moving species, or fish with long fins. It is also best to avoid housing multiple Arowanas together unless the tank is exceptionally large — territorial conflicts between individuals of the same species can be quite severe.
Breeding
Breeding Osteoglossum bicirrhosum in an aquarium is an extremely difficult task (difficulty 4 out of 5), and successful cases in home settings are exceedingly rare. The main challenge is the enormous space required for pair formation and spawning.
The Silver Arowana is a paternal mouthbrooder: after spawning, the male collects the fertilized eggs in his mouth and incubates them for 50–60 days. During this entire period, the male does not eat, devoting himself entirely to protecting his offspring. Arowana eggs are among the largest of any freshwater fish — approximately 1.5 cm in diameter. The fry remain in the father's mouth even after hatching and only leave once they reach 7–10 cm and have fully absorbed their yolk sacs.
In the wild, spawning coincides with the onset of the rainy season, when water levels rise and flood riverside areas. Attempts to stimulate spawning in captivity involve large water changes with soft, cool water to mimic the arrival of rains, but successful breeding requires ponds or pools with volumes of several thousand liters. Sex determination in Arowanas is difficult — males generally have a larger and wider mouth, adapted for carrying offspring.