Silver Arowana

The silver arowana belongs to the primitive bonytongue family. Its long, flat body is covered in large silver scales; with its large upturned mouth and the two barbels on its chin, it glides just below the surface. In the wild it hunts insects, spiders and even small birds on branches by leaping up to two meters out of the water, which is why it is also called the "water monkey."

Stores sell 10 cm juveniles; it reaches 30–40 cm in the first year and 90 cm as an adult. For this reason it is unsuitable for most homes.

It lives near the surface in the flooded forests and still backwaters of the Amazon.

• Volume: at least 1500 liters for an adult; the width of the aquarium should be at least 1.5 times the fish's length so it can turn (a 250 cm × 100 cm footprint). In a narrow aquarium its eyes and jaw become unhealthy.
• Lid: a sturdy, heavy lid is essential; arowanas jump out of the aquarium and get injured.
• Water: 26–29°C, soft to slightly acidic, very clean. Strong filtration.
• Setting: a quiet room; sudden movements and changes in light startle it and cause it to crash into the glass.

Carnivorous; it hunts from the surface. Shrimp, fish fillet, crickets and insects, arowana pellets. Live feeder fish (guppies, goldfish) are not recommended: they carry disease and create nutritional imbalances.

It eats anything that fits in its mouth. It is aggressive toward its own kind.

Good companions: in a very large aquarium, large bottom- or mid-dwelling fish too big for its mouth: large plecos, oscars, a school of silver dollars, large catfish.

Avoid: small fish, shrimp, a second arowana.

In a home aquarium a single fish is kept. In public aquariums, aggression is spread out in very large systems with 5 or more arowanas; this is not recommended for the home.

The male incubates the large fertilized eggs in his mouth and carries the fry there until their yolk sacs are used up. It almost never breeds in the aquarium.

• Drop eye: the eye turning downward; associated with a narrow aquarium and constant feeding from below.
• Jaw and gill cover deformities: poor water and insufficient space.
• Jumping injuries: in an uncovered aquarium or one with a weak lid.

The sexes are hard to tell apart externally; mature males may be slimmer and have larger anal fins.