Osteoglossum bicirrhosum (Silver Arowana)

Overview

The Silver Arowana, often referred to in German as "Gabelbart" (fork-beard), is an iconic, prehistoric-looking freshwater fish. Known for its massive size and surface-dwelling habits, it is a highly sought-after centerpiece for monster fish keepers. Due to its specific needs, it requires a dedicated and experienced aquarist.

Distribution and Habitat

Native to the Amazon River basin in South America, this species thrives in slow-moving waters, flooded forests, and swamps. They are specifically adapted to hunting near the water's surface, where they leap to catch insects and small prey from overhanging branches.

Description of Silver Arowana

Body shape:

They possess an elongated, laterally compressed, and ribbon-like body that allows them to glide effortlessly just below the water's surface.

Color:

Juveniles often have a bluish tint, but adults develop a brilliant, uniform metallic silver coloration with large, distinct, armor-like scales.

Barbels:

They have two distinct, fleshy barbels protruding from the tip of their lower jaw, which act as sensory organs to detect vibrations on the water surface.

Snout:

The snout features a steep, upward-pointing (superior) mouth with a pronounced lower jaw, perfectly designed for surface feeding.

Eyes:

Their large eyes are positioned to look upward, though they are prone to a condition called "drop eye" in captivity if their diet or environment is suboptimal.

Fins:

The dorsal and anal fins are exceptionally long, starting near the middle of the body and extending almost all the way to the caudal peduncle.

The Tail:

The tail (caudal fin) is relatively small and rounded, seamlessly blending with the overall streamlined profile of the fish.

Temper

While inherently predatory, they are generally peaceful toward tank mates that are too large to be considered food. However, they can be highly territorial towards other Arowanas.

Sociality

They are best kept as solitary centerpieces or in a massive community tank with other large, robust species like large catfish, pacus, or large cichlids. Any fish small enough to fit in their mouth will be eaten.

Activity

Silver Arowanas are active, constant swimmers that patrol the upper levels of the aquarium. They are also notorious and powerful jumpers, often leaping to catch prey or when startled.

Keeping and Caring for Silver Arowana

Tank size:

A massive aquarium is required. A minimum of 250 gallons (approx. 1000 liters) is needed for an adult, with a footprint of at least 8 feet long and 3 feet wide to allow them to turn comfortably.

Water Parameters:

Temperature

Keep the water warm, ideally between 24-28°C (75-82°F).

pH

They prefer slightly acidic to neutral water, with a pH range of 6.0 to 7.0.

Hardness

Soft to moderately hard water is best, ranging from 1 to 8 dGH.

Ammonia, Nitrite, Nitrate

Ammonia and Nitrite must be strictly at 0 ppm. Nitrates should be kept below 20 ppm through large, regular water changes, as they are highly sensitive to poor water quality.

Lighting

Moderate to dim lighting is preferred. Sudden bright lights can startle them, causing them to jump and potentially injure themselves.

Water flow

A moderate water flow mimics their natural riverine environment and helps keep the tank well-oxygenated without pushing them around.

Decorations and Plants

The upper half of the tank must remain completely open for swimming. Bottom decorations like smooth rocks and driftwood are fine. A heavy, tightly secured lid is the most critical piece of equipment to prevent jumping.

Diet

They are carnivorous surface feeders. In captivity, they should be fed a varied diet of high-quality floating pellets, insects (crickets, mealworms), earthworms, and occasional thawed frozen fish or shrimp.

Some Feeding Tips

Avoid feeding them mammalian or avian meats (like beef heart or chicken), as they cannot digest the fats properly. Feed juveniles once or twice a day, and adults every other day to prevent obesity and water fouling.

Breeding

Silver Arowanas are paternal mouthbrooders. The male carries the eggs and fry in his mouth for several weeks. Breeding in home aquaria is exceedingly rare due to the monumental tank size required for a compatible pair to spawn.

Conclusion

The Silver Arowana is a breathtaking "monster fish" that offers a rewarding experience for expert aquarists. If you have the space, budget, and dedication to meet their enormous housing requirements, they make a truly majestic and lifelong aquatic pet.