Longhorn Cowfish
Lactoria cornuta
The Toxic Horned Box (20 inches / 50 cm). Adorable, goofy, and curious. But it grows massive, swims poorly due to its rigid bone shell, and acts as a biological weapon.
Water Temperature
22 - 26 °C
pH Value
8.1 - 8.4
Water type
Freshwater
Tank level
Bottom and middle
Adult size
45 cm
Minimum tank volume
>= 500 L
Minimum group
>= 1
GH
1 - 12 dGH
KH
1 - 6 dKH
TDS
25 - 240 ppm
Conductivity
39 - 375 uS/cm
Species description
Geographical Origin and Habitat: MARINE. Indo-Pacific (from the Red Sea and East Africa, to Indonesia, up to Japan). Inhabits calm coastal estuaries, harbors and seagrass meadows on sandy/muddy bottoms.
Taxonomy and Morphology: Longhorn Cowfish (Lactoria cornuta). Iconic and bizarre: rigid body encapsulated in a bony carapace, "calf" snout and, above all, two long protruding frontal "horns" (and two posterior ones).
Social Behavior: Slow and clumsy swimmer (uses only the small fins for propulsion, helicopter style). Peaceful towards other fish and curious. Establishes a strong bond with the owner who feeds it, following him from the glass.
Coloration and Sexual Dimorphism: Background ranging from sandy yellow to bright olive yellow/green. Studded with beautiful blue ocellated spots. In case of stress it can fade into a pale beige. No externally identifiable sexual dimorphism.
Care, breeding and tankmates
Aquarium Setup: Huge Fish Only With Live Rock (FOWLR) tank (min. 500 liters / 130 gallons). Warning: the aquarium must have MEDIUM/SLOW water flow. Blasted currents would make it crash against the rocks, seriously injuring it given its poor swimming skills.
Diet and Feeding: Voracious omnivore. Sweeps the bottom blowing away the sand. Provide gel foods, nori algae, chopped clam/mussel pulp (to wear down the beak teeth) and mysis. Frequent but measured meals.
Water Quality: Standard marine quality but ZERO tolerance for thermal shock. Pay attention to wavemakers (protect the grills): swimming badly, they risk being sucked in and remaining trapped, killing themselves.
Compatibility and Cohabitation: NOT Reef-Safe: will devour polychaetes, snails, shrimp and peck at corals. Tankmates must be very calm (Batfish, Seahorses or Anthias). Forbidden Triggerfish, pufferfish and fast Surgeonfish that would stress it.
Aquarium Breeding: Impossible. Pelagic species that releases floating eggs in the open sea at sunset (Haremic serial spawners).
Risks and Diseases: TOXIC BOMB. Like boxfish, if severely stressed, sick or scared to death, it can release Ostracitoxin through the skin: a poisonous foam that will kill all the fish in the tank in a few minutes.
Geographic Origin and Distribution
MARINE. Indo-Pacific (from the Red Sea and East Africa, to Indonesia, up to Japan). Inhabits calm coastal estuaries, harbors and seagrass meadows on sandy/muddy bottoms.
Origin
Tropical oceans and reefsNorth AmericaAfrica and MadagascarSouth and Southeast AsiaEast Asia
Fish profile
- Temperament
- Semi-aggressive
- They are docile, curious, and can become quite tame, often learning to beg for food from their owners. They are never aggressive towards other peaceful species. Their main danger is the toxin they can release when heavily stressed or bullied.
- Diet
- Omnivore
- They are omnivorous benthic feeders that graze on invertebrates, algae, and sponges in the wild. In the aquarium, they need a varied diet of meaty foods like squid, clam, and mysis shrimp, along with marine algae. Offering hard-shelled foods helps keep their continuously growing teeth ground down.
- Life expectancy
- 8-12 years
- Under optimal care, the Longhorn Cowfish (Lactoria cornuta) has a lifespan of 8 to 12 years. Their longevity is closely linked to stable water parameters and proper nutrition, as they are highly sensitive to sudden environmental changes. Stress management is critical, as this species can release a deadly toxin (ostracitoxin) when highly stressed or dying, which can wipe out the entire aquarium. Providing a large, calm environment is essential for their long-term health and survival.
- Adult size
- 45 cm
- The catalog's scalar value is 45 cm. The FishBase SPECIES table (v25.04 snapshot) source reports a maximum adult measurement of 46 cm for this species, recorded as total length (TL). The taxonomic record consulted is Lactoria cornuta (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
- Solitary
- They are best kept individually in a home aquarium due to their massive spatial requirements. Keeping multiple cowfish often leads to severe aggression between conspecifics. A single specimen makes a fantastic, interactive wet pet.
- Feeding frequency
- Twice daily
- They should be fed small portions two to three times a day. Because they are slow, deliberate eaters, make sure faster fish do not steal their food. Target feeding is often necessary to ensure they receive adequate nutrition.
- Bioload
- The Longhorn Cowfish produces a very heavy bioload, especially as it grows to its massive adult size. A heavy-duty protein skimmer and large biological filters are strictly required. Frequent, large water changes are vital for maintaining acceptable water quality.
- Flow
- Stagnant
- They are notoriously weak and clumsy swimmers. They require areas of low to moderate water flow where they will not be blown around the tank. Avoid strong powerheads that could trap or exhaust them.
- Reproduction
- Oviparous
- Breeding the Longhorn Cowfish in a home aquarium has not been successfully achieved. They are pelagic spawners that release eggs and sperm into the open water column. The larval stage is incredibly difficult to sustain in captivity.
- Compatibility & tankmates
- They are peaceful, slow-moving fish that should not be kept with fast, aggressive, or fin-nipping species. They must be kept with calm companions to avoid stress. Crucially, when stressed or dying, they can release ostracitoxin, a potent poison capable of wiping out the entire tank.
- Tank level
- Middle/Bottom
- They explore all levels of the aquarium but spend significant time near the substrate hunting for food. They often blow jets of water into the sand to uncover hidden prey. They require a very large, open tank to maneuver their rigid bodies.
Scientific Parameters & Models
FishBase
Window to the official scientific data of the species
Data synced on: 06/15/2026
- Trophic level
- 3.5 ± 0.37 se
- Resilience
- High (less than 15 months)
- Phylogenetic uniqueness (PD50)
- 0.5625
- Bayesian Length-Weight
- a = 0.02042, b = 2.76
- VulnerabilityModerate vulnerability (36 / 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.
