Black Rhom Piranha (2.75-4”)

Scientific Name: Serrasalmus rhombeus

Maximum Size & Lifespan:
The Black Rhom Piranha is one of the largest Serrasalmus species, capable of reaching 15-18" in length. In captivity, with proper care, they can live 15–20 years, making them a long-term commitment.

Recommended Aquarium Size:
A minimum of 120–180 gallons (450–570 liters) is required for a single adult, with more space always beneficial due to its size, strength, and activity level. Juveniles can be raised in a 30-90 Gallon tank for better observation.

Water Changes & Care:

• Temperature: 75–82°F (24–28°C)

• pH: 6.0–7.5

• Water Changes: 30–50% biweekly/weekly to maintain excellent water quality.
  Strong filtration and high oxygenation are essential. Black Rhoms are sensitive to deteriorating water conditions, and poor quality can lead to stress and disease.

Tankmates:
Not recommended. Serrasalmus rhombeus is highly aggressive, especially as it matures, and will usually attack or kill other fish. Best kept alone as a display specimen.

Diet:
Carnivorous predator with opportunistic feeding habits. In captivity, feed a varied diet of:

• Frozen shrimp and tilapia
  

• With time and multiple feeding attempts carnivore pellets/sticks are a food option for the Black Rhom. It is never guaranteed they will accept dry foods. 
  

Overview:
The Black Rhom Piranha is a powerful, solitary predator admired for its imposing presence and striking, dark metallic sheen that can range from gunmetal gray to jet black depending on age and lighting. Juveniles tend to be lighter with speckled flanks, darkening with age. Their territorial nature, especially in smaller spaces, makes them a true “one-fish” specimen for experienced keepers only.

Natural Environment:
Native to rivers and floodplain lakes of the Amazon and Orinoco basins in South America, often found in slow to moderate flowing waters with submerged wood and root tangles. Water is typically soft and acidic, with low visibility in some regions. They are ambush predators, using cover to surprise prey.

Breeding:
Breeding Serrasalmus rhombeus in captivity is extremely rare and largely undocumented. They are solitary and highly territorial, making pairing dangerous. In the wild, related species scatter eggs in shallow vegetated areas during the rainy season. Captive breeding attempts often fail due to aggression and difficulty in sexing adults.