白锯脂鲤 · Black Piranha/Rhom

Overview

Serrasalmus rhombeus is known under both black- and white-piranha names. Deep red eyes characterize mature fish, but geographic forms differ markedly in shape, color, and eventual size. Unresolved population or species boundaries may be involved. Individual housing is the appropriate default.

Distribution & habitat

Traditional records span much of northern South America, but the actual range is disputed and some localities may concern other species.

Adults favor larger, deeper channels and areas near rapids. Young more often occupy quiet, densely vegetated margins. Fish from turbid whitewater tend to be paler than clearwater or blackwater forms.

Aquarium setup

A single adult needs a footprint around 210 × 45 cm or larger. Supply ample oxygen, sand, and some wood or roots for shelter. Plants can be attempted but may be bitten.

Excellent water quality is necessary, with weekly changes up to about half the volume. External or inline heating reduces opportunities for equipment damage; a heater left inside needs a strong guard.

Diet & feeding

Wild fish opportunistically consume fins, flesh, small fishes, insects, crustaceans, and carrion. Plant consumption established for certain relatives should not automatically be attributed to this species.

Most individuals gradually accept nonliving foods. Young can receive worms, brine shrimp, and chopped shrimp; adults take larger shellfish, shrimp, squid, fish flesh, and earthworms. Two or three meals weekly generally suffice after maturity. Newly introduced fish may initially refuse food and require observation during adjustment. Avoid unnecessary feeder fish and large quantities of terrestrial meat.

Behaviour & compatibility

Mixed housing is unsuitable, and fighting between conspecifics may continue until only one remains. Isolated accounts of coexistence with armored catfishes or other members of the species do not establish long-term safety.

Sexual dimorphism

Dependable routine external differences are lacking. Females in spawning condition are generally fuller, but ordinary body shape alone is inconclusive.

Breeding

Captive reproduction is rare, with aggression and insufficient space major obstacles. A historical zoo spawning occurred in a large planted installation, with eggs deposited among aquatic moss and the surrounding area defended. Eggs were removed for separate rearing.

Some young were returned a year later and reportedly tolerated initially, then attacked after reaching around 15 cm. This individual account does not establish stable cohabitation between parents and offspring.

Notes

Juveniles without the mature red eye are easily misidentified. Diamond, high-back, and jet-black trade labels may mix locality claims with appearance. Neither a seller's locality nor one color feature should be used alone to determine identity.