Green Terror

Family: Cichlidae Green Terror, Aequidens rivulatusAequidens rivulatusPhoto © Animal-World: Courtesy Greg Rothschild
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My female terror hates my male terror and does not want to be closed with him what shall i do  BIBEK

An exotic beauty, the mature Green Terror will display a rainbow of exquisite colors!

The Green Terror Aequidens rivulatus is a most beautiful fish with an overall green and blue metallic sheen. In addition, they have a magnificent array colors that can be purple, pink, red and/or electric blue. The males are the most colorful of this species and develop a brilliant red edging on their tail fin, but the the females are also quite striking.

This species tends to be confused with its very similar looking relative, the Blue Acara Aequidens pulcher. For a time it was actually known as the A. pulcher, but is now recognized as an independent species. Though they look very similar in many aspects, there are some key differences between these two fish.

In color the Blue Acara is mostly a steel blue-gray, with less of the green sheen seen on the Green Terror. The Green Terror is larger, reaching up to about 10 - 12" (25 - 31 cm) in length in the wild, while the slightly smaller Blue Acara only gets to be about 8 inches (20 cm). A mature Green Terror develops a more pronounced hump on its head while the Blue Acara retains a more sloped forehead. In addition,  the Green Terrors are also significantly aggressive than the Blue Acara (one of the reasons for the name "Terror").

This colorful cichlid is a hardy fish that is moderately easy to care for. It's a rewarding specimen for the more experienced aquarist to keep as long as the water quality is maintained and they are provided a high quality diet. They are a ready feeder and if bred they become excellent parents, though they are known to sometimes be a bit lax with their first clutch of eggs.

As is typical with most large cichlids, the Green Terror is aggressive and requires a large aquarium. When young they can readily be kept in a community tank with other South American cichlids, but as they mature the become very belligerent and should be seperated into their own tank or into a tank with similarly sized and aggressive tank mates. They need at least 30 to 40 gallons of space just for themselves when kept as a single fish. As a pair they will need at least 75 gallons or more so as not be so aggressive, and even larger if kept with other large similarly aggressive tankmates.

The aquarium water should be neutral to slightly acidic, a little on the softer side, and have a moderate amount of current. They are fine with normal lighting and a gravel substrate. Provide lots of rockwork with caves and hiding places but be sure to leave an open area for swimming. Sunken driftwood can be used not only as a decoration but also as a water conditionting agent to help keep pH down in a too neutral aquarium. 

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

Geographic Distribution
Aequidens rivulatus
Data provided by
  • Kingdom: Animalia
  • Phylum: Chordata
  • Class: Actinopterygii
  • Order: Perciformes
  • Family: Cichlidae
  • Genus: Aequidens
  • Species: rivulatus
Green Terror Again

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Short video of a fairly large and colorful Green Terror

The video showcases both sides of this large and vibrantly colored Green Terror. With the lack of a bump on the head, it seems we are looking a female Green Terror. Quite a few nice shots and closeups!

Green Terror - Quick Aquarium Care
  • Size of fish - inches: 12.2 inches (30.99 cm)
  • Minimum Tank Size: 40 gal (151 L)
  • Temperament: Aggressive
  • Aquarium Hardiness: Moderately hardy
  • Temperature: 70.0 to 80.0° F (21.1 to 26.7° C)
  • Aquarist Experience Level: Intermediate
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Habitat: Distribution / Background

The Green Terror Aequidens rivulatus was described by Gunther in 1860. They are found in South America; western Ecuador and central Peru. This species is not listed on the IUCN Red List.

They inhabit rivers, starting at the Pacific slope from the Esmeraldas River in Ecuador to the Tumbes River in Peru. Though, there is some speculation that the species in the Esmeraldas may not actually be a Green Terror but instead is its own distinct species, but this has not yet been fully substantiated. They are absent from many coastal streams that contribute a higher pH, as this is something Amazonian cichlids cannot handle. These fish inhabit the mostly still waters of both turbid and clear flowing stream basins where they feed on worms, crustaceans, and insects.

  • Scientific Name: Aequidens rivulatus
  • Social Grouping: Pairs - The females will sometimes become extremely aggressive towards their mate, particularly during spawning, so keep a constant eye on their behaviors.
  • IUCN Red List: NE - Not Evaluated or not listed


The Green Terror is a deep bodied fish with pointed anal and dorsal fins. They are a good sized cichlid and tend to reach just over 12 inches (31 cm) in the wild, though in the aquarium they are typically about 6–8 inches (15 - 20 cm) and have a life span of about 7 - 10 years, though there are reports of them living more than 10 years if well cared for.

This is a very colorful deep bodied fish marked with various striping on its body and face. The male has a green and blue metallic sheen, a blue anal fin, and a red band at the edge of its tail fin. In addition, mature males will develop a rounded hump on their heads. The female has a darker tone with a green anal fin, no red band along the edge of its tail fin, and are generally a little smaller than the male.

All cichlids. along with some saltwater fish such as wrasses and parrotfish, share a common feature of a well-developed pharyngeal set of teeth located in the throat, along with their regular teeth. Cichlids have spiny rays in the back parts of the anal, dorsal, pectoral, and pelvic fins to help discourage predators. The front part of these fins are soft and perfect for precise positions and effortless movements in the water as opposed to fast swimming.

Cichlids have one nostril on each side while other fish have 2 sets. To sense "smells" in the water, they suck water in and expel the water right back out after being "sampled" for a short or longer time, depending on how much the cichlid needs to "smell" the water. This feature is shared by saltwater damselfish and cichlids are thought to be closely related.

  • Size of fish - inches: 12.2 inches (30.99 cm) - In the wild the maximum size for these fish is about 12.2 inches (31 cm). Males will reach up to about 10 - 12" (25 - 31 cm) and females will reach 7 - 9" (18 - 23 cm). In the aquarium the typical size is smaller at about 6–8 inches (15 - 20 cm).
  • Lifespan: 10 years

Fish Keeping Difficulty

Although the Green Terror is a stunning fish and draws the attention of all levels of fishkeepers, it may not be for everyone. They are large and extremely aggressive fish, requiring a large amount of space to themselves and are only suitable for similarly large and aggressive tank mates. In pairs, particularily, they are known to "terrorize" (hence their name) the other fish in their aquarium. In addition, the Green Terror is extremely sensitive to water condition changes and needs a very stringent maintenance schedule. Due to these restrictions and obstacles, it is recommended that Green Terrors be housed by fish keepers with a significant amount of experience in keeping large and aggressive cichlids. That being said, this fish is still able to thrive and do well in an aquarium maintained by a begginner as long as that beginner is diligent in maintenance and knowledgeable concerning size and tank mate restrictions. 

  • Aquarium Hardiness: Moderately hardy
  • Aquarist Experience Level: Intermediate

Foods and Feeding

The Green Terror is primarily a carnivore that can be fed a variety of foods, but they do tend to be picky. They will eat frozen foods like krill, bloodworms, and brine shrimp as well as flakes, plankton and green vegetables. They can also be fed cichlid pellets. For the best color offer live red earthworms.

Do not feed beef hearts or other red meats to this fish, foods high in protein can cause issues in the digestive system.

Feed young fish 2 to 3 times a day and adults 1 to 2 times a day. Feeding in smaller amounts several times a day instead of a large quantity once a day will keep the water quality higher over a longer time. All fish benefit from vitamins and supplements added to their foods.

  • Diet Type: Carnivore
  • Flake Food: Yes
  • Tablet Pellet: Yes
  • Live foods (fishes, shrimps, worms): Most of Diet
  • Vegetable Food: Some of Diet
  • Meaty Food: Most of Diet
  • Feeding Frequency: Several feedings per day

Aquarium Care

The Green Terror are fairly easy to care for provided their water is kept clean, though they are very sensitive to deterioating tank conditions. To help combat this sensitivity, make sure to use an efficient biological filter coupled with a stringent maintenance schedule. Aquariums are closed systems and regardless of size all need some maintenance. With home aquariums the nitrate and phosphates build up over time and the water hardness increases due to evaporation. Because these fish are very sensitive to pollutants and pH instabilty, it is important that at least 15 - 20% of the tank water should be replaced bi-weekly, and weekly if the tank is densely stocked. When doing the weekly water changes always use a gravel cleaner to make sure all of the decomposing organic matter that has built up is removed. Condition replacement water properly and try to match the temperature of the tank water as close as possible. The majority of of problems that occur with tropical fish tanks usually come down to one cause, decomposing organic matter!

Use an algae magnet or scraper to keep viewing panes clear.

  • Water Changes: Bi-weekly - 15 - 20%, weekly if tank is well stocked.

Aquarium Setup

As with all large South American cichlids, Green Terrors need a lot of room, 30 or 40 gallons for an individual fish. A minimum of 75 gallons is suggested for a pair. An even larger aquarium will be needed if keeping them together with other large fish. They do best in water that is soft and slightly acidic to neutral. Provide low to moderate water movement and efficient biological filtration. They are fine with normal aquarium lighting and enjoy lots of rockwork with caves and hiding places. Use driftwood to help pull the pH down if you have very hard water. Be sure to leave an open area in the center for swimming.  If setting up a large tank with other species, make sure to arrange the tank to block lines of sight as this will help divide the tank into "territories" and help quell aggressive tendencies. 

  • Minimum Tank Size: 40 gal (151 L) - 40 for a single fish and 70 for a pair.
  • Substrate Type: Large Gravel
  • Lighting Needs: Moderate - normal lighting
  • Temperature: 70.0 to 80.0° F (21.1 to 26.7° C)
  • Breeding Temperature: - 77 - 79° F (25 - 26° C)
  • Range ph: 6.5-8.0
  • Hardness Range: 5 - 13 dGH
  • Water Movement: Moderate
  • Water Region: All

Social Behaviors

As with all larger South American cichlids, adequate tank space is the most important element in lowering aggression. The Green Terror is a highly to moderately aggressive cichlid that can be kept with other large South American cichlids. Depending on their personality and the circumstances in which they grow up, they can actually end up relatively peaceful. They use their lateral line to determine how much space they have available to them, if they have "too little" they often become rather aggressive as adults; contrarily, if they have "enough" they tend to not be as aggressive once matured. With a bigger tank they have less of a need to "take someone out" so that they will have room to grow.

The Green Terror is generally aggressive toward those of the same species. It is possible that the female Green Terror is more aggressive than the males and should be kept singly unless breeding. If breeding, they will become very aggressive and need a very large tank or a tank of their own. Do not house with Green Terrors with African Cichlids as the Africans are too small and will be harassed or eaten.  Green Terrors can be kept with Pacus, Plecostomus, Oscars, Silver Dollars, Gars, and other similarly sized fish and of a like temperment.

  • Venomous: No
  • Temperament: Aggressive
  • Compatible with:
    • Same species - conspecifics: Yes - Good if kept in pairs.
    • Peaceful fish (): Threat
    • Semi-Aggressive (): Threat
    • Aggressive (): Threat
    • Large Semi-Aggressive (): Threat
    • Large Aggressive, Predatory (): Monitor
    • Slow Swimmers & Eaters (): Threat
    • Shrimps, Crabs, Snails: Threat - is aggressive
    • Plants: Monitor - Will uproot plants that are not secure.

Sex: Sexual differences

There are a few differences between male and female Green Terrors, including the red band around the male's tail fin. In addition, males will have blue anal fins while females have green anal fins, males tend to be a bit larger than females, and males will develop large, rounded humps on their heads while the females will not. One unique aspect of the Green Terror females is that they are actually more aggressive than the males, particularily when spawning. Normally this tendency is switched. 

Breeding / Reproduction

The Green Terror has been successfuly bred in captivity for many years. They are egg layers and open breeders, meaning the female deposits the eggs and the male fertilizes them in the open water. To ensure you have at least one viable male/female pair, it is recommended to obtain several juveniles and allow them to pair up at their own pace. The breeding water should be slightly acidic with a pH of 6.5, soft to medium- hard at between 4 - 12° dGH, and have temperatures between 77 - 79° F (25 - 26° C). The parents will clean off a flat rock to spawn on and will lay up to 400 eggs. The fry hatch in 3 - 4 days and are free swimming by 11 days. during which time the parents will both be attentive and protective of their young. Perform frequent water changes. Feed fry newly hatched brine shrimp, crushed flake, and fry food. The fry grow slow initially until about 1/2 to 3/4 inches (2 cm) but then will grow at an accelerated pace. See a general description of how cichlids breed in: Breeding Freshwater Fish: Cichlids.

  • Ease of Breeding: Moderate

Fish Diseases

Green Terrors are subject to infections as well as other diseases that affect ail freshwater fish, especially if the water is of poor quality and low oxygenation. One common problem is Ich. It can be treated with the elevation of the tank temperature to 86° F (30° C) for 3 days. If that does not cure the Ich, then the fish needs to be treated with copper (remove any water conditioners). Several copper based fish medications are available for Ich. Copper use must be kept within the proper levels, so be sure to follow the manufacturers suggestions. A copper test also can be used to keep the proper levels. You can also combine increasing the temperature with an Ich medication treatment.

Hard water will contribute to the notorious Head and Lateral Line Erosion (HLLE) or 'Hole-in-the-Head' disease, an ailment that large cichlids are prone to. Intestinal disease can be treated with metronidazol.

As with most fish the Green Terror Cichlids are prone to skin flukes and other parasitic infestations (protozoa, worms, etc.), fungal infections, and bacterial infections. 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.

Anything you add to your tank can bring disease to your tank. Not only other fish but plants, substrate, and decorations can harbor bacteria or harmful chemicals. 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.


The Green Terror is readily available both online and in fish stores. They are moderately priced as juveniles and become slightly more expensive at they mature.


Author: Carrie McBirney, Clarice Brough CFS
Lastest Animal Stories on Green Terror

BIBEK - 2013-01-01
My female terror hates my male terror and does not want to be closed with him what shall i do

  • Jeremy Roche - 2013-01-02
    What size tank is it?  They may need more space.  Try adding some decor if size is not the issue and re-arranmge the decor that is in there now.  Sometimes the change will make them calm down and give them areas to hide.
J/K Ranch - 2009-03-19
I had a beautiful Green Terror named Quervo. The story of how I bought Quervo is interesting, I've had every kind of fish and consider myself an expert when it comes to water quality, compatibility, equipment use, medicines, etc.

To change things up, I picked up a small 5" African Lungfish to put it in a 75 gallon tank. While Ramses was small, I tried different fish to see if they would get along much less survive and I quickly learned the answer would be no.

I tried an Arowana, Jack Dempsey, and many others. I even put in two Leaf Fish thinking the Lung Fish wouldn't see the 'dead leaves' floating and if he did, would ignore them. Nope, he got them too.

The last one was Quervo, the striking Green Terror. In a 75 gallon with a 5" Lungfish, I was told (and thought) most any fish, especially one swimming in the upper part of the tank, would do fine.

The first day they were together was uneventful. The Lungfish knew there was company and made a couple of quick moves but the Terror was too fast and aware of it's 'company'. The second day, I watched the Lungfish move like a missile and push the Green Terror so I quickly prepared the 30 gallon for Quervo though it would take a couple of days for water quality to be set.

That night, Ramses struck Quervo and bit a piece of Quervo's back. I though it was done, weak swimming, lethargic, etc. Instead, he came back and did so with vigor. His back seemed to regenerate and I kid you not, it had a certain swagger as it swam by the Lungfish and maneuvered itself in a confident manner.

I ended up leaving it in the tank and honest to God, they became the best of tankmates. Anything else I added, one of them would take out. They both grew to where they went into a 180 which is where they stayed for years.

To this day, I have a special affinity for Green Terrors.

  • Dirk - 2010-12-16
    If you informed yourself a tiny bit, before buying a fish, you should have known that the Lungfish is VERY territorial.
Avaneesh Samant - 2009-03-09
My big colorful green terror is alone in my 60 gallon tank, it's about 8 inches. He has killed a lot of fish, even an oscar and a pleco! These fish are actually docile while they are juveniles but when they grow up, they *attain* the title of 'Green Terror' and actually terrorize the tank! But, this fish is extremely beautiful (more beautiful when they are adults) and are quite intelligent. They tend to form a bond with the owner and get really excited when the owner arrives! One of the most beautiful fish I've ever seen. They love to show off their color and are very active. A beautiful fish, good for beginners (provided the tank is large enough), and eat anything given to them.
*Tip* - If you want to enhance the colour of your green terror, feed him a varied diet of blood worms, pellet food and vegetable matter everyday... and they grow very fast too...

Tara - 2008-05-31
The Green Terror is an absolutely wonderful and beautiful cichlid. I currently have two males. One is nine inches and housed in a 75 gallon tank...alone. The tank is decorated with driftwood, rocks, and various plants. He's alone because he has not played well with others since he was approximately five inches long. At seven inches he was such a "terror" that I had to assign him his own home. The other is six inches and is housed in a 75 gallon with a dempsey and convict. I can't detect a tank leader, though the dempsey seems to be the most aggressive. But neither the terror or convict have ever really backed down when the dempsey shows aggession. Theres some posturing, flaring, but rarely more than that. The nine inch terror is named "Damien". The other terror is "Orion". The dempsey is named "Rambo" and the convict is "Capone". The two Green Terrors are the most personable and in many ways remind of Oscars in terms of how they interact with me. They are always the first to notice my approach and are always "dancing" to get my attention. Over the years I have owned various cichlids, everything from Oscars to Red Devils. Through it all the Green Terror has always been a constant in my aquarium tanks.

terri - 2009-07-10
First, I want to compliment Animal-World for such an insightful, informative, and comprehensive Internet site on a myriad of pet interest. To the point, I currently house a pair of Green Terrors in a 125 gallon aquarium, with an Oscar, Convict, Raphael Cat, and Pleco. Green Terror are wonderful fish. I find them to be comparable to Oscars and Red Devils in terms of personality and owner interaction. I've had mine for a little more than two years. They are named Caesar and Cleo (Cleopatra), and have been paired for about eighteen months. They have spawned numerous times over the years. I've sold some of their young, gifted some to friends, donated some to the local LFS, fed some to my other fish, and am currently raising some of their fry in a 40 gallon breeder. I love cichlids, and house everything from Angelfish to Red Devils, Convicts and Oscars to Green Terrors and Red Terrors. I've been maintaining aquariums for more than 25 years and would recommend the Green Terror to anyone who is interested in a personable, interactive, and aggressive fish.

  • Sandy Griffiths - 2011-09-23
    Hi I have a 160 litre tank 3 ft and I have 2 convicts an oscar and a golden tip rivoulatis male. I think was wanting some advice on them they seem to be breathing heavily and are not eating or growing much Im not sure what im doing wrong. This is my fish tank so I'm clueless. I have a 1250 aquies filter I clean the tank once a week use the water nuetralizer they have a big rock to hide in and 2 fake trees they also dont seem to be growing my friend has 2 oscars which were bought at the same time as mine and her oscars are about double if not closs to triple the size as mine i am feeding them fish pellets and once a week a little bit of ox heart. I have tested the ph and it was between 7- 6.6 and the temp is set at 28 degrees i have a uv light which is left on during the day and turned off at night please help as i have no idea whats wrong
david - 2009-11-28
Got a green terror today, he is in a 55g with 2 aquaclear 110s ( total 1000gph) which turns the tank over a total of 18.18 times an hour. He is with 10 giant danios and doesn't bother them at all, but after all he is only 3.5 inches. He ate about 10 minutes after I put him in the tank which is outstanding for the first day. He has strong coloring and is very healthy so far. He is very active, exploring the tank, digging holes, moving gravel etc. Great fish and this website helped very much!


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