Wolf Fish / Traíra

Geographic Origin and Biotope: Extremely widespread from Costa Rica down to Argentina. Survives everywhere: lakes, rivers, cold streams but particularly in muddy stagnant pools without oxygen (has auxiliary lungs).

Taxonomy and Morphology: Common Wolf Fish / Tararira (Hoplias malabaricus). The "lesser" cousin of the Aimara, but equally prehistoric. Cylindrical torpedo morphology, jaws full of retractable needle-like teeth. Grows "only" up to 50-60 cm (20-24 inches).

Social Behavior: Nocturnal ambush predator. Spends 90% of its time on the dark bottom motionless as a log, waiting. Unlike the Aimara, it is much more passive towards the aquarist and does not break the glass.

Coloration and Sexual Dimorphism: Mud color, gray/brown, with irregular camouflage shades to blend in with rotting vegetation. Opalescent or golden scary eyes. Males more tapered.

Aquarium Setup: Large and wide tanks (min. 150 cm / 60 inches). Bottom possibly in sand for abrasions. It is a lethargic fish but with a deadly jump: watertight and heavy lids are the only guarantee not to find it dried out on the floor. Likes a lot of partial shade (woods and floating plants).

Diet and Feeding: Totally Carnivorous. Feeding it is easy but polluting: fish steaks, shelled shrimp, massive sinking pellets for carnivores. Less of a "chewer" than the aimara, it tends to swallow prey (or fingers) whole in a fraction of a second.

Water Quality: The immortal. A fish capable of surviving in nature in swamps that dry up by crawling in the mud breathing air. In the aquarium it forgives almost any nitrate surge or pH crash, but clean water prevents rot.

Compatibility and Tankmates: Will swallow in the night any fish that fits in its mouth. It can (not always) be paired with very robust fish with a very high profile that it cannot swallow: large Astronotus, large Doradids (Megalodoras) and Pacus. Risk is always very high.

Aquarium Reproduction: Very difficult due to space (ponds are needed). Males dig large pits (craters) in the mud, attract the female there to lay thousands of eggs and protect them fiercely by assaulting even birds (or humans) that approach the nest.

Risks and Diseases: Starvation from refusal of dry food. Many Wild specimens will let themselves starve rather than accept dead foods (frozen shrimp or pellets). The aquarist must arm himself with a lot of patience for weaning (wiggling the food).