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Wolf Fish / Traíra
Hoplias malabaricus
A prehistoric, armored freshwater monster. Reaches over 50 cm (20+ inches) of pure muscle and bone-crushing jaws. An incredibly aggressive, nocturnal apex predator that will literally bite the owner's hand. Only for serious 'Monster Fish' keepers with massive tanks.
- Taxonomy
- Class:ActinopteriOrder:CharaciformesFamily:ErythrinidaeGenus:HopliasSpecies:Hoplias malabaricus
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Water Temperature
22 - 28 °C
pH Value
6 - 8
Water type
Freshwater
Tank level
Bottom and middle
Adult size
50 cm
Minimum tank volume
>= 500 L
Minimum group
>= 1
GH
4 - 15 dGH
KH
2 - 7 dKH
TDS
80 - 295 ppm
Conductivity
125 - 461 uS/cm
Species description
Geographical Origin and Habitat: 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.
Care, breeding and tankmates
Aquarium Setup: Large and wide tanks (min. 150 cm / 60 inches). Bottom possibly in sand for abrasions. It is a 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 Cohabitation: 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 Breeding: 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).
Geographic Origin and Distribution
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).
Origin
Extra-Amazon South AmericaCentral America and Caribbean
Fish profile
- Temperament
- Semi-aggressive
- This is a highly aggressive and territorial species that does not tolerate intruders in its space. They are notorious for being fiercely aggressive not only towards other fish, but occasionally towards the aquarist during tank maintenance. Extreme caution must be exercised when keeping this formidable predator.
- Diet
- Omnivore
- In the wild, they are apex predators feeding almost exclusively on live fish and large invertebrates. In captivity, they can often be trained to accept frozen meaty foods such as whole shrimp, fish fillets, and mussels. A varied, high-protein carnivorous diet is essential for their long-term health and growth.
- Life expectancy
- 9-15 years
- The Common Wolf Fish is a hardy species that can live for 9 to 15 years in a home aquarium under proper care. To achieve a long lifespan, it is important to maintain stable water parameters and avoid feeding them fatty foods. Providing a low-stress environment with dim lighting and secure hiding places also supports their health. A tight-fitting lid is essential, as they are known to jump out of the water, which is a common cause of premature death.
- Adult size
- 50 cm
- The catalog's scalar value is 50 cm. The FishBase SPECIES table (v25.04 snapshot) source reports a maximum adult measurement of 65 cm for this species, recorded as total length (TL). The taxonomic record consulted is Hoplias malabaricus (v25.04); male or unsexed record. These figures are not interchangeable: the first is the profile's editorial reference, whereas the second is a published maximum under a specific measurement convention; differences among sources can reflect sex, population, life stage and measuring method.
- Sex ratio
- Pair
- There are no easily identifiable external differences between males and females outside of the breeding season. Females may appear slightly more robust or rounder when actively carrying eggs. Due to their aggressive nature, keeping multiple individuals together to form pairs is highly risky.
- Feeding frequency
- Twice daily
- Juveniles should be fed a small meaty meal once every day or two. As they mature into large adults, feeding frequency should be reduced to once every two to three days. Overfeeding should be avoided to prevent excessive water fouling and obesity.
- Bioload
- This species produces a very high bioload due to its massive size and carnivorous diet. They consume large, messy meals which result in significant amounts of biological waste. Therefore, heavy filtration and frequent water changes are mandatory to maintain safe water parameters.
- Flow
- Stagnant
- They generally prefer areas with sluggish to moderate water movement, mimicking their natural calm river habitats. Strong currents should be avoided as they are ambush predators that rely on remaining stationary. Gentle surface agitation is sufficient for maintaining appropriate oxygen levels.
- Reproduction
- Oviparous
- Breeding this species in home aquaria is exceptionally rare due to their extreme aggression and large space requirements. In their natural habitat, they construct shallow pits in the substrate where eggs are deposited. The male is highly protective of the nest and will aggressively guard the fry until they become independent.
- Compatibility & tankmates
- They are highly predatory and will readily consume any tank mate that fits into their mouth. It is highly recommended to keep this species in a dedicated species-only aquarium. If tank mates are absolutely necessary, they must be significantly larger and robust enough to avoid predation.
- Tank level
- Middle/Bottom
- They are predominantly bottom-dwelling ambush predators that spend much of their time resting on the substrate. They will often hide among submerged wood, rocks, or dense vegetation waiting for prey. However, they will quickly strike upwards towards the middle or top levels when actively feeding.
Scientific Parameters & Models
Window to the official scientific data of the species
Data synced on: 06/15/2026
- Trophic level
- 4.5 ± 0 se
- Resilience
- Low (4.5 - 14 years)
- Phylogenetic uniqueness (PD50)
- 0.5
- Bayesian Length-Weight
- a = 0.00891, b = 3.1
- VulnerabilityHigh to very high vulnerability (66 / 100)
Image gallery
Licensed images linked to the species or, when marked, to the closest representative taxon.
Related species
Recommendations grouped by close relatives, companion choices, and similar care.
