Aequidens rivulatus (Green Terror Cichlid)

Aequidens rivulatus

Last updated on August 13th, 2022 at 06:07 pm

The Aequidens rivulatus (green terror cichlid) is among the most popular South American cichlids, and not without reason! Because it’s hardy and easy to keep, this fish makes an excellent choice for both beginners and experienced hobbyists alike.

One thing you should know about the Aequidens rivulatus, however, is that it can grow very large; this means you need to have plenty of room in your tank if you want to keep them!

Learn more about this interesting fish and its captive care requirements below.

Origin and descriptions

Aequidens rivulatus

Aequidens rivulatus is a species of freshwater fish in the family Cichlidae. It is endemic to South America and found in Peru, Colombia, and Venezuela. Its natural habitat is rivers. They may grow up to 12 inches in length if they are kept properly.

The Aequidens rivulatus, or green terror cichlid, are carnivorous by nature and will eat all kinds of invertebrates such as snails, worms, mussels, and crayfish. The smaller fish will also eat flakes, pellets, and freeze-dried foods to help get their nutrients.

Their temperament is very aggressive and should be kept only with large tropicals that can handle them. Some have been known to attack humans, so caution should be used when handling them. To breed them you will need at least a 100 gallon tank with lots of places for both parents to hide when not actively protecting eggs or fry.

Species profile

Aequidens rivulatus

Aequidens rivulatus are native to South America and thrive in water between 72 and 80 degrees Fahrenheit. These fish are known for their territoriality but can be housed with other non-aggressive species such as convict cichlids, silver dollars, or angelfish. They should never be kept with aggressive cichlids like Oscars, Jack Dempsey’s, or puffers.

Green terrors prefer tanks decorated with rocks and logs to hide in. They feed on both plant matter and meaty foods like shrimp and earthworms; they may even nip at each other while feeding if kept together without adequate space. In order to maintain optimal health levels, Aequidens rivulatus requires frequent partial water changes every week to ten days depending on how many you have in your tank.

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As a freshwater fish, it is native to South America, and lives in rivers, lakes, and ponds in Bolivia, Brazil, Paraguay, and Argentina. This fish can grow up to 12 inches long. It is a powerful predator that will eat anything it can fit into its mouth. They should not be kept with other similar-sized predators because they will not tolerate competition for food or space.

Green terror cichlid size

They can grow up to 12 inches (30 cm) in length.

Aequidens rivulatus tank size

The minimum recommended tank size to house an Aequidens rivulatus is 50 gallons.

Tank set up

A tank that is 50 gallons or larger is recommended for keeping an Aequidens rivulatus. This fish will tend to dig around in rocks and gravel, so it is best to provide plenty of places for it to hide. A lower pH level of about 7.0 is ideal for keeping these fish happy and healthy.

Keep nitrate levels below 20 ppm and make sure to keep your water warm at about 78 degrees Fahrenheit; do not allow your water temperature to drop below 65 degrees. Be careful if you have other large fish species that are rough with each other as they can end up hurting each other over territories.

The Aequidens rivulatus is omnivorous and likes meaty foods like brine shrimp, tubifex worms, and bloodworms as well as greens such as spirulina, algae wafers, seaweed disks, and even cucumber. They may also enjoy peas once in a while.

You should feed them two to three times per day when they are young and then just one time a day once they reach adulthood. Be careful when feeding them as their jaws contain razor-sharp teeth which can cut through food easily, resulting in injury by cross-contamination. Feeding them smaller portions of food more frequently is ideal for making sure that all goes according to plan.

Green terror tank mates

South American cichlids are extremely territorial fish and must be housed in a tank that is at least 50 gallons in size. Due to their territorial nature, they should not be housed with other species of fish. They should not be housed with other large South American cichlids; if you have more than one of these fish in your tank, they will fight each other and may kill one another.

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Some good tank mates are other South American cichlids; large tetras, such as Silver Hatchetfish; Plecostomus fish; catfish. These fishes should be added to your tank before you add your Aequidens rivulatus. Do not house these fish with small tetras, as they will eat them! If you must have these two species in your tank, choose larger tetras and keep a close eye on them until you know for sure that there is no aggression.


Aequidens rivulatus

With proper care, a mated pair of green terrors can produce as many as 1,000 fries in two years. As with all cichlids, sex is easy to determine when they are young. However, once they become adults males are very difficult to tell apart from females and care must be taken not to accidentally kill breeding fish.

To breed green terrors, you will need a male and female pair that have been in good health for several months. The water should be soft (1 dGH or less) with a pH above 7.5 and an ideal temperature range between 23 and 26 degrees Celsius (74-79 degrees Fahrenheit). A sandy substrate at least four inches deep is also required along with large amounts of rocks or decorations for them to dig pits.

While most breeders provide some type of spawning area such as a pit dug by their fish, green terrors will often excavate their own if one isn’t provided. After being conditioned with live foods, a separate tank containing fine-grain black sand may be used while performing frequent partial water changes. Eggs can be fed crushed flake food upon fertilization.

Green terror fry grows extremely quickly, so daily feeding is essential until they reach juvenile size.

Are Aequidens rivulatus aggressive or peaceful?

The Aequidens rivulatus (green terror cichlid) is aggressive. Green Terrors tend to be more peaceful when kept in larger groups of 6 or more fish, however, if kept in smaller groups they may become territorial and/or aggressive towards other tank mates.

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Aequidens rivulatus care

Aequidens rivulatus

Aequidens rivulatus are highly sensitive to water conditions, so they will likely only thrive in a properly maintained aquarium. In addition, they require very large tanks (ideally 50 gallons or more). They also need highly oxygenated water and a variety of hiding places. More aggressive than most other cichlids, green terrors can be kept with some other large fish that enjoy similar conditions. Good tankmates include jack dempseys and red devils.

What do Aequidens rivulatus eat?

Green terrors are omnivores, so you’ll need to feed them both meaty foods and plants. A varied diet for these fish will include bloodworms, brine shrimp, krill, and even some plant-based flakes. You can find bloodworms or brine shrimp at most pet stores.

For green terrors that weigh less than 1.5 pounds, a weekly feeding of live feeder fish (goldfish are often used) is recommended; if your green terror is larger than 1.5 pounds, twice-weekly feedings of live goldfish should suffice.

Green terrors get really excited when they see food; to prevent your goldfish from being injured by overzealous predators, place a few rocks in front of your tank before doling out any food.

Water parameters

Aequidens rivulatus

The ideal water condition should have a pH 6.5-7.0, hardness 10-20dH, temperature 22-26 degrees C (72-79 degrees F) (may be raised to 28 degrees C/82 degrees F over time).

The tank should have plenty of swimming space and rocks to perch on with caves and crevices for retreat. They should not be kept in small tanks where they will feel insecure.

The water should preferably contain sand or gravel at a depth of 5-10cm/2-4 in. The tank should also contain a cover as these fish are able to jump or climb out of their tank if there is no cover in place.

Aequidens rivulatus lifespan

This fish can live up to 10 years in captivity. In its natural habitat, it reaches maturity at age 2 but rarely lives more than 6 years.

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Parasites and diseases

Green terrors are relatively disease-resistant and don’t tend to suffer from a high incidence of parasites. However, if you keep your fish in a non-cycled tank, it’s possible that they will pick up some type of parasite. The parasites will cause symptoms such as erratic swimming and lethargy. In severe cases, these parasites can kill their host fish.

If your green terror has contracted a parasite or is showing any of these signs, quarantining is highly recommended until you have identified what is causing them to be sick.


The green terror is typically known as a very pugnacious fish. It can be seen patrolling its territory in search of prey items such as fish, shrimp, and snails. However, they will generally leave their own kind alone when they are not competing for food or spawning areas. They are also preyed upon by other species of fish.

Some common predators are Red-tailed Black Shark, Otocinclus Catfish, and Scissortail Goby.

The cichlids known as Red-Tailed Black Sharks should be avoided at all costs, as they will decimate a green terror aquarium.

Do Aequidens rivulatus make good pets?

Green terrors have been a popular choice of freshwater fish for aquarium owners due to their bright colors and large size. They can live up to 10 years with proper care, and make an excellent addition to any planted aquarium due to their fierce appetite for algae.

Green terrors will consume almost anything in your tank, so be careful not to overfeed them. Like many larger fish, green terrors should only be kept with other species of similar size as they can get nippy when they’re bored or hungry.