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. 3 1/2 feet is their largest size, while a more common length for them to is up to 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 though, and may reach about 12 - 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 the one big problem in keeping these as a pet, is they grow fast and they get huge. The Pacu soon outgrows all but the largest aquariums. They are generally sold as juveniles and 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 tank mates. The young are a little more aggressive than adults. But an adult, even though peaceful, will 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 650 gallons and upwards of a 1000 gallons or more to house an adult. The tank should also have extra thick glass. Black Pacus have been known to literally swim through the sides of an aquarium when spooked.
As their home must be so large, it limits the people who should keep one. Some people have kept Black Pacus in heated, indoor ponds. But due to their dark color they really can’t be appreciated when housed this way. However, if you have the space to provide for a huge tank, they are easy to keep.
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 know by are Pacu, Black-finned Pacu, Black-finned Colossoma, Giant Pacu, Cachama and Gamitana.
They have been 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 the United States of North America.
They are solitary, and as juveniles they live in the black waters of flood plains, feeding on insects, snails, and decaying plant matter. Adults move to the flooded forest areas for the initial few months of the flood season, and feed on fruits and grains.
Scientific Name: Colossoma macropomum
Social Grouping: Solitary - They are loners as adults.
IUCN Red List: NE - Not Evaluated or not listed
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). 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. Its fins are black. It is often confused with the Piranha when small. As juveniles they are almost identical in appearance, but 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 will jut out more 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 it is common for them to reach only about 27 1/5 inches (70 cm).
Lifespan: 25 years - They have a lifespan of between 20 -25 years in the captivity.
Fish Keeping Difficulty
Black Pacu are large fish and should only be cared for in commercial aquariums or by the most experienced fish keepers with the space and financial ability to care for these giants. They are actually very hardy and easy to care for. The 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. The size alone limits who will able to keep one as they would need an aquarium upwards of a 1000 gallons.
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 and 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 if you plan on having any other fish living with your Black Pacu, make sure that they 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
Pacus are big messy fish that need ample filtration. Water changes of about 30 - 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 - 50% water change every other week.
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 can handle a variety of water conditions. They need clean water, so good filtration is important and a moderate water flow.
They will mostly occupy the middle of the aquarium so 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 a panic like reaction from them, causing them to 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 bit smaller tank, but they grow fast 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
Water Movement: Moderate
Water Region: Middle - These fish will swim in the middle of their home.
As adults they are solitary fish, but not aggressive. The young tend to be a little more boisterous with tank mates than adults. But an adult, even though peaceful, may eat anything that’s small enough to fit into their mouths. This fish will do best kept in its own tank or with other similar sized non-territorial species. They are generally peaceful, they have been known to nip fins on occasion so tank mates should not be too aggressive nor to timid.
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 (): Monitor
Shrimps, Crabs, Snails: Safe - not aggressive
Sex: Sexual differences
Males have a sharper extension on the dorsal fin, their anal fin is toothed, and they can be brighter colored than the female.
Breeding / Reproduction
The Black Pacu has not been bred in the aquarium, though it has been successfully artificially bred in captivity as a fishery specimen. Presumably it would be very difficult due to their large size and space needs. Induced breeding has been done with the use of hormones at research facilities, first reported in 1992 to 1993 at the Fish Culture Station in Natal, Brazil. For a description of breeding characin fish, see Breeding Freshwater Fish: Characins.
Ease of Breeding: Difficult - Captive breeding of pacus is unknown in the home aquarium.
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 bring disease to your tank. 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 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 you deal with it at an early stage. When keeping 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 give them a well balanced diet. The closer to their natural habitat the less stress the fish will have, making them healthier and happy. 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. It is recommended to read up on the 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.
The Black Pacu or Tambaqui are commonly available. Be sure of what you are getting thouygh, as they are often confused with the almost identical looking Piranha when small.
J Bartnick - 2014-12-06 I found your article on Black Pacu's very interesting though I disagree with many of your requirement for keeping Pacu's. I have had my two Black Pacu's for 21 years in a 170 aquarium. I do water changes (1/3) about every 3 to 4 months. Temperature in winter time is between 60 & 70 degrees. They are fed once a week (every Monday) using Koi pellets. If the water is not changed for 5 or 6 months the Pacu's will develop a white film over the eyes, etc. A quick water change resolves the problem. They have quit growing - size of aquarium? Probably. They swim mostly along the bottom of the tank which is covered with 1/2 inch of gravel. Joy to watch. Healthy to boot. Hope they do not live longer that 25 years. That is a lot of tank cleanings !!!!
Clarice Brough - 2014-12-08 I love Pacu's and it sounds like you have some cool fish. The information provided on this page is to provided optimal care for these hardy fish. That in turn gives them the best chance to not only thrive, but to reach their full potential, up to 42 inches in length. Obviously with a fish this big, the 700 - 1000 gallons that is suggested is definitely needed. It sounds like your fish could be stunted due to the size of the tank, cold water winter temperatures, and the limited feedings. Such reduced feeding does help keep the bioload down though, and then the more frequent water changes aren't needed... but yeah, you will have a lot of water changes even with 170 gallons!
Raleigh - 2014-04-11 I have a pacu fish but it won't eat. Can someone tell me why not?
Jasmine Brough Hinesley - 2014-04-12 How long as that been going on? Is it showing any other symptoms of illness? I would keep an eye on it. In the meantime, check all the water parameters (water quality and temperature) and make sure they are appropriate. Also do a partial water change if it has been a while since the last one.
Anonymous - 2012-01-25 Hi, my science teacher is giving me her red bellie pacu and I plan on keeping it in a 150 gallon tank with 3 senegal bichirs, 4 fire mouth cichlids, some kind of darter, some mosquito fish, and 4 feeder fish. I will introduce the fish thruogh out the period of 1-3 months. the pacu is presently 8-10 inches and blind in it's left eye. My teacher feeds it flakes and live fish from time to time. Are there any fish I could also put in the tank to keep the pacu away from the other fish and can I change its diet to mostly veggies and some meat, no live fish included. P.S., can you keep a pacu with piranhas?
Charlie Roche - 2012-01-25 It's great your science teacher is giving you a Pacu but is he giving you a tank to go with him?> A Pacu when an adult is going to go about 3/12 feet and weigh about 60 pounds. You need a thousand gallon tank. If it will fit in his mouth, he will eat it. Pacu with Piranhas - I guess it is whoever gets bigger first. Piranhas will eat anything. Did your science teacher ever read up on what he was doing?
Anonymous - 2012-01-26 The store person said it wouldn't get bigger than its tank, the store person lied.
Charlie Roche - 2012-01-27 I don't know whether he store person 'lied' or just mis informed. Fish not out growing their tank is a myth - an old wives tale used to sell more fish. In any case he is not a good or reliable informtion source.
kye turnbull - 2013-05-13 a fish will grow slower in a small tank but will still get big
Lola - 2014-01-11 Hello...I have a black pacu and a red bellied pacu in a 150 gal. tank and they have busted the top canopy! You MUST have a very large tank for these fish. I am currently trying to relocate mine....really put thought into this before getting them. However they are wonderful pets...I hand feed and pet mine everyday, but I just can't house them anymore. I have had them 2 years and have went from about 3 inches and a few oz. up to 20 inches from nose to fin tip and 11 inches from belly to back and around 10 or 12 pounds.
Jim Sadler - 2014-02-05 The Pacu can no longer be considered a safe fish. In New Guinea they have killed native people as well as threatening to exterminate the crocodile population. The black Pacu is doing well in South Florida fresh water canals and can be quite a shock when they strike a bait as they are strong. A 53 lb. black Pacu died when a cold spell hit and it got into the salt water rivers here. They are good news for fishermen and apparently reproducing well.
Clarice Brough - 2014-02-06 Fortunately, Pacu's kept in a very large aquarium are probably not going to be attacking anyone.