Black Pacu

Pacu, Tambaqui, Black-finned Pacu

Family: Characidae Colossoma macropomumPhoto © Animal-World: Courtesy Ken Childs

The Black Pacu may be a member of the Characin family, but it's nothing like the average Tetra!

The Black Pacu Colossoma macropomum, also known as the Tambaqui, is a characin just like such favorites as the Neon Tetra and the Glolight Tetra. However, that is where the similarities end. This fish is the largest characin found in South America and barely resembles most of its characin cousins. 

Reaching a size of 3 1/2 feet (108 cm) in length and weighing over 60 pounds in the wild, the Black Pacu is an impressive fish. Though 3 1/2 feet is their largest size, they are more commonly found to be about 27 1/5 inches (70 cm). Another Pacu found in the aquarium trade is its close relative, the Red-bellied Pacu Colossoma brachypomum. This species is a bit smaller, reaching between 12 and 24 inches (30-61 cm). Other common names for the Black Pacu are Black-finned Pacu, Pacu, and Giant Pacu.

The Black Pacu is interesting, personable, very hardy, and easy to feed. This makes it sound like the perfect aquarium fish. Unfortunately, they can pose a problem for aquarists in that they grow very big very fast and can soon outgrow all but the largest aquariums. They are generally sold as juveniles and are often mistaken for the similar looking Piranha. Although these two fish are close relatives, the Pacu is not an aggressive predator like the Piranha and generally has a more peaceful demeanor with tankmates. The young are a little more aggressive than adults, though even the most peaceful adult will still eat anything small enough to fit in its mouth.

The Pacu is definitely a specialty fish. To keep one, you will need an aquarium of at least 650 gallons and preferably upwards of a 1000 gallons or more with extra thick glass. Black Pacus have been known to literally swim through the sides of an aquarium when spooked.

The large size of the aquarium they require limits the people who should keep one. Some people have kept Black Pacus in heated, indoor ponds, but their dark color makes them difficult to appreciate when housed this way. However, in a large enough tank, they are easy to keep.

For Information on keeping freshwater fish, see:
Freshwater Aquarium Guide: Aquarium Setup and Care

Habitat: Distribution / Background

The Black Pacu Colossoma macropomum, also known as the Tambaqui, was described by Cuvier in 1816. They are found throughout much of the Amazon and Orinoco River basins in South America. This species is not listed on the IUCN Red List. Other common names it is known by are Pacu, Black-finned Pacu, Black-finned Colossoma, Giant Pacu, Cachama, and Gamitana.

They were introduced in New Guinea as a food source in 1994 to the Sepik River, and in 1997 to the Ramu River. They have also been introduced in multiple countries: in South America including Bolivia, Peru, Colombia, Brazil, and Venezuela; in Central America including Cuba, Dominican Republic, Honduras, Jamaica, and Panama; and in North American in the United States.

Black Pacu are solitary fish. As juveniles, they live in the black waters of flood plains, feeding on insects, snails, and decaying plant matter. Adults move to flooded forest areas during the initial months of the flood season and feed on fruits and grains. Fin nipping is also a common method of feeding among juveniles and young adults.

• Scientific Name: Colossoma macropomum
• Social Grouping: Solitary - They are loners as adults.
• IUCN Red List: NE - Not Evaluated or not listed

Description

The Black Pacu can get up to get up to 42.5 inches (106 cm) in length and weigh up to 66 pounds (30 kg). They usually won't attain that length in the aquarium, however, it is more common for them to reach only about 27 1/5 inches (70 cm) in captivity. The body of the adult Pacu is very deep and laterally compressed with a slight arch to the back. They have a life span of 20 to 25 years in the aquarium.

This species is gray to black, sometimes with spotting in its mid section, and the fins are black. It is often confused with Piranha when small since Black Pacu juveniles are almost identical to them. However, as the Black Pacu matures, it becomes more rounded and wider than the Piranha. The easiest way to tell the difference when they are young is that the jaw of the Piranha juts out further than that of a Pacu.

• Size of fish - inches: 42.5 inches (107.95 cm) - These fish get up to 4 1/2 feet (106 cm) and weigh up to 66 pounds (30 kg) in the wild, but in captivity, they usually reach only about 27 1/5 inches (70 cm).
• Lifespan: 25 years - They have a lifespan of between 20 and 25 years in the captivity.

Fish Keeping Difficulty

Black Pacu are large fish and should only be housed in commercial aquariums or by the most experienced fish keepers with the space and financial ability to care for these giants. The size alone limits who will able to keep one as they would need an aquarium upwards of a 1000 gallons.

Aside from their need for space, they are actually very hardy and easy to care for. They are not very picky about aquarium water conditions and are used in aquaculture because they can live in mineral-poor waters and are very disease resistant.

• Aquarium Hardiness: Very Hardy
• Aquarist Experience Level: Advanced - The aquarist must be prepared to maintain a tank upwards of a 1000 gallons to house an adult fish.

Foods and Feeding

The Black Pacus are omnivores. In the wild, they will consume fruits, grains, insects, snails, detritus, and plant matter. In the aquarium, they will readily eat most anything and can be offered frozen foods as well as a pellet diet. Aquarium-kept specimens may also eat fish, so make sure that any of the Black Pacu's tankmates are considerably larger than its mouth.

• Diet Type: Omnivore
• Flake Food: No
• Tablet / Pellet: Yes
• Live foods (fishes, shrimps, worms): Some of Diet
• Vegetable Food: Some of Diet
• Meaty Food: Some of Diet
• Feeding Frequency: Several feedings per day

Aquarium Care

Pacus are big, messy fish that need ample filtration. Water changes of about 30 to 50% are needed every other week, depending on the bio load, to keep this fish very happy and healthy.

• Water Changes: Bi-weekly - Do a 30 to 50% water change every other week.

Aquarium Setup

The Black Pacu is an extremely large fish. Because of their large adult size, they need a very large aquarium. Juveniles can be kept in a smaller tank, but they grow quickly when well fed and will soon need a much larger tank. If you have a 1000+ gallon tank at your disposal, they are easy to keep. They are hardy and quite disease resistant, so they can handle a variety of water conditions. They need clean water, so good filtration is important, and they prefer a moderate water flow.

They will mostly occupy the middle of the aquarium where they need a spacious open area for swimming. Provide a decor of plants, roots, and driftwood to help them feel comfortable and provide them with some hiding places. They are known to be a little skittish. Fast movements or vibrations can cause them to panic and bang into the sides of the tank, heater, or anything else in the aquarium.

• Minimum Tank Size: 634 gal (2,400 L) - Juveniles can be kept in tanks that are a bit smaller, but these fish grow quickly and will soon need at least 634 gallons, with 1000 gallons or more being best.
• Suitable for Nano Tank: No
• Substrate Type: Any
• Lighting Needs: Moderate - normal lighting
• Temperature: 74.0 to 82.0° F (23.3 to 27.8° C)
• Range ph: 5.0-7.8
• Hardness Range: 2 - 15 dGH
• Brackish: No
• Water Movement: Moderate
• Water Region: Middle - These fish will swim in the middle of their home.

Social Behaviors

As adults, they are solitary fish but not aggressive. The young tend to be a little more boisterous with tankmates. But an adult, while peaceful, may eat anything small enough to fit into its mouth. This fish will do best kept in its own tank or with other, similar sized, non-territorial species. They are generally peaceful but have been known to nip fins on occasion, so tankmates should be neither too aggressive nor too timid.

• Venomous: No
• Temperament: Peaceful
• Compatible with:
  • Same species - conspecifics: Yes - May swim in schools when young, but adults are loners.
  • Peaceful fish (): Monitor - Only other large community fish should be kept with the Pacu to avoid becoming a meal.
  • Semi-Aggressive (): Threat
  • Aggressive (): Threat
  • Large Semi-Aggressive (): Threat
  • Large Aggressive, Predatory (): Threat
  • Slow Swimmers & Eaters (): Threat
  • Shrimps, Crabs, Snails: Safe - not aggressive
  • Plants: Safe

Sex: Sexual differences

Males have a sharper extension on the dorsal fin, a toothed anal fin, and they can be more brightly colored than the females.

Breeding / Reproduction

The Black Pacu has not been successfully bred in the aquarium. Presumably, breeding them would be very difficult due to their large size and space needs. In captivity, they have been artificially bred as a fishery specimen. Induced breeding accomplished through the use of hormones at research facilities was first reported around 1992 or 1993 at the Fish Culture Station in Natal, Brazil. For a general description of breeding characin fish, see Breeding Freshwater Fish: Characins.

• Ease of Breeding: Difficult - Captive breeding of Pacus is unknown in the home aquarium, but as a fishery specimen, they have been artificially bred through the use of hormones.

Fish Diseases

Like most giant fish, the biggest concern with the Black Pacu is lack of space and food. If you can meet these needs, not much goes wrong with these giants. These fish are hardy, and disease is not usually a problem in a well-maintained aquarium. That being said, there is no guarantee that you won't have to deal with health problems or disease. Anything you add to your tank can introduce disease. Not only other fish but plants, substrate, and decorations can harbor bacteria. Take great care and make sure to properly clean or quarantine anything that you add to an established tank so as not to upset the balance. Because these fish eat live food, disease can be passed to them from their foods. Make sure to quarantine live food before feeding.

A good thing about the Black Pacu is that due to their resilience, an outbreak of disease can often be limited to just one or a few fishes if dealt with at an early stage. With more sensitive types of fish, it is common for all fishes to be infected even before the first warning signs can be noticed. The best way to proactively prevent disease is to give your fish the proper environment and a well-balanced diet. The more closely their environment resembles their natural habitat, the less stress the fish will have, making them healthier and happier. A stressed fish is more likely to acquire disease.

As with most fish the Black Pacu are prone to skin flukes, parasitic infestations (protozoa, worms, etc.), ichthyobodo infection, parasitic infestations (protozoa, worms, etc.), bacterial infections (general), and bacterial disease. Aquarists should read up on common tank diseases. Knowing the signs and catching and treating them early makes a huge difference. For information about freshwater fish diseases and illnesses, see Aquarium Fish Diseases and Treatments.

Availability

The Black Pacu or Tambaqui are commonly available. Be sure of what you are getting, though, as they are often confused with the almost identical looking Piranha when small.

References

• Animal-World References: Freshwater Fish and Plants
• Dr. Rüdiger Riehl and Hans A. Baensch, Aquarium Atlas Vol. 1, Publisher Hans A. Baensch, 1991
• Glen S. Axelrod, Brian M. Scott, Neal Pronek, Encyclopedia Of Exotic Tropical Fishes For Freshwater Aquariums, TFH Publications, 2005
• Joseph S. Nelson, Fishes of the World, Wiley, 2006.
• Colossoma macropomum (Cuvier, 1816) Cachama, Fishbase.org

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