FishFreshwaterExpert
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Red-tailed Barracuda
Acestrorhynchus falcatus
The 'Dog Characin'. A ruthless open-water predator (up to 30 cm) armed with massive, protruding canine teeth. A hyper-active swimmer that requires enormous tanks, intense water flow, and massive tankmates to prevent it from eating everyone.
Water Temperature
24 - 28 °C
pH Value
6 - 7.5
Water type
Freshwater
Tank level
Surface and middle
Adult size
27 cm
Minimum tank volume
>= 2,000 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: Predator widely distributed in the Amazon and Orinoco basins. Hunts in slow-flowing rivers, oxbows and lowland lakes, hiding among submerged branches and sandbanks waiting to ambush prey.
Taxonomy and Morphology: Known as the Freshwater Barracuda or Dog Characin. Large characin (27 cm / 11 inches) with an incredibly hydrodynamic torpedo-shaped body. Equipped with a monstrously large mouth armed with canine-like fangs visible even with the jaws closed.
Social Behavior: Surprisingly peaceful and shy towards conspecifics and fish too large to be swallowed. Being a pack ambush hunter, it should always be kept in small groups (4-5 specimens) to alleviate stress and prevent panic attacks and fatal jumps.
Coloration and Sexual Dimorphism: Camouflage and silvery, with green or yellowish holographic reflections on the back. It features a dark teardrop-shaped spot behind the gill cover and a black spot at the base of the tail, often rimmed with red (Red-tailed Barracuda). Adult females are much stockier and gravid.
Care, breeding and tankmates
Aquarium Setup: Given its size and speed in the predatory dash, it requires very long tanks (minimum 150 cm / 5 feet). Set up with dark sandy bottoms and a tangle of suspended roots where they can hide. A heavy, sealed lid is mandatory: they are formidable ballistic jumpers.
Diet and Feeding: Obligate piscivore. The transition to dead food is the hardest obstacle: wild-caught fish will only accept live small fish (Guppies, Danios, etc.). With immense patience, they can be accustomed to slices of silversides, giant bloodworms and shrimp tails offered via forceps.
Water Quality: Requires very clean water and oversized filtration to manage the high protein load of the diet. Temperature 24-28°C (75-82°F), slightly acidic or neutral pH (6.0 - 7.5), medium-low hardness. Does not tolerate ammonia or nitrite spikes, which corrode the fragile fins.
Compatibility and Cohabitation: Harmless towards any fish that does not physically fit in its mouth. Excellent for mixed tanks of large Characins (Metynnis, large Leporinus), large Loricariids and quiet terrestrial Cichlids (Geophagus, Satanoperca). Will instantly ingest any fish under 10 cm.
Aquarium Breeding: Exceptional and non-standardized event. In nature they are seasonal pelagic spawners that scatter their eggs in tides and currents, not caring for the offspring. The fry are ruthless cannibals from their first day of free swimming.
Risks and Diseases: Common deaths caused by stress during transport (banging against the glass fracturing the snout) or fatal jumps out of the tank. Susceptible to internal parasites resulting from careless feeding with infected live feeder fish.
Geographic Origin and Distribution
Predator widely distributed in the Amazon and Orinoco basins. Hunts in slow-flowing rivers, oxbows and lowland lakes, hiding among submerged branches and sandbanks waiting to ambush prey.
Origin
Tropical oceans and reefsAmazon, Orinoco, and Guianas
Fish profile
- Temperament
- Peaceful
- Acestrorhynchus falcatus is a predatory species but is surprisingly peaceful and non-aggressive towards tank mates that are too large to be eaten. However, they are highly skittish and nervous, meaning they can easily injure themselves by crashing into decor or the aquarium glass when startled. They show schooling instincts and are much calmer when kept in a group of their own kind. They do not establish strong territories, though they will assert dominance during feeding.
- Diet
- Carnivore
- This species is an obligate piscivore, meaning its natural diet consists almost entirely of smaller fish and occasionally river shrimp. In captivity, they should be transitioned from live feeder fish to high-quality frozen foods like silversides, shrimp, krill, and chopped fish fillets. Offering mammalian or avian meats is highly discouraged as they cannot properly digest these fats. With patience, some specimens can be trained to accept carnivore pellets, though fresh or frozen aquatic proteins remain the best choice.
- Life expectancy
- 5-10 years
- In captivity, Acestrorhynchus falcatus typically has a lifespan ranging from 5 to 10 years when provided with optimal care. Achieving maximum longevity depends heavily on maintaining pristine water quality, offering a high-quality carnivorous diet, and providing a stress-free environment. Because they are highly active and easily startled, a large, peaceful tank is crucial to prevent stress-related illnesses and injuries that can shorten their lives.
- Adult size
- 27 cm
- The catalog's scalar value is 27 cm. The FishBase SPECIES table (v25.04 snapshot) source reports a maximum adult measurement of 30 cm for this species, recorded as total length (TL). The taxonomic record consulted is Acestrorhynchus falcatus (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
- Group
- There is no distinct sexual dimorphism, making it difficult to establish a specific male-to-female ratio for Acestrorhynchus falcatus. However, they are schooling fish that feel much more secure when kept in groups of four to six individuals. Keeping them in groups helps diffuse intraspecific aggression and reduces their naturally skittish behavior. If kept singly, they can become overly stressed and prone to injuring themselves.
- Feeding frequency
- Once daily
- Juveniles should be fed daily to support their rapid growth and development. Adult Acestrorhynchus falcatus do not need to be fed every day, and feeding them every other day or three to four times a week is sufficient. Overfeeding can lead to water quality degradation and health issues like fatty liver degeneration. It is best to feed them in small portions that they can consume immediately to prevent uneaten food from decaying in the tank.
- Bioload
- Medium to High
- Acestrorhynchus falcatus has a relatively high biological waste output due to its predatory nature and purely carnivorous diet. These fish consume protein-rich meals, which leads to increased ammonia and nitrate levels in the water column. Consequently, they require robust filtration systems with a flow rate of at least 4 to 5 times the aquarium volume per hour. Regular weekly water changes of 30% to 50% are essential to maintain the pristine water quality they need to thrive.
- Flow
- Strong
- Acestrorhynchus falcatus inhabits flowing rivers and streams in the wild and prefers moderate to strong water currents in the aquarium. A steady flow not only mimics their natural habitat but also encourages active swimming and helps reduce their skittishness. Powerheads or filter outlets can be positioned to create a directional current, leaving some calmer zones where they can rest. Excellent water oxygenation, which often accompanies good water flow, is also vital for this active species.
- Jump risk
- Yes
- This species poses an extremely high jump risk, especially when startled or chasing live prey near the surface. Acestrorhynchus falcatus are powerful and fast swimmers capable of launching themselves completely out of the water. It is absolutely necessary to equip their aquarium with a heavy, tight-fitting lid with no open gaps. Floating plants can also help cover the surface and reduce the fish's impulse to jump by providing a visual boundary.
- Reproduction
- Oviparous
- Breeding Acestrorhynchus falcatus in captivity is exceptionally difficult, and there are very few documented cases of successful aquarium spawning. In the wild, reproduction is seasonal and heavily tied to environmental changes, such as the onset of the rainy season, which triggers schooling and spawning in flooded areas. In a home aquarium, simulating these complex seasonal variations, including changes in temperature, conductivity, and water levels, requires specialized knowledge and large setup systems.
- Compatibility & tankmates
- Aggressive
- Acestrorhynchus falcatus can be kept with other medium to large, peaceful fish that are too large to be swallowed. Ideal tank mates include larger characins, catfish, cichlids like Oscars or Severums, and active bottom-dwellers. They must not be housed with small, slender fish, as these will be quickly hunted and eaten. When keeping Acestrorhynchus falcatus, it is best to maintain them in a group of their own species to encourage natural behavior and decrease stress.
- Tank level
- Top/Middle
- Acestrorhynchus falcatus primarily inhabits the middle and upper levels of the water column, where they actively patrol for prey. They are pelagic predators that require ample open swimming space to perform fast, sudden bursts of swimming. While they spend most of their time in open water, they also benefit from tall plants or driftwood placed along the perimeter of the tank to provide shelter when they feel threatened.
Scientific Parameters & Models
FishBase
Window to the official scientific data of the species
Data synced on: 06/15/2026
- Trophic level
- 4.2 ± 0.73 se
- Resilience
- High (less than 15 months)
- Phylogenetic uniqueness (PD50)
- 0.5001
- Bayesian Length-Weight
- a = 0.00759, b = 3.12
- VulnerabilityLow vulnerability (20 / 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.
