Green terror

Quick facts

Adult size

25 cm

Lifespan

can live up to 12 years

Tank zone

mid-bottom

Temperament

aggressive

Difficulty

intermediate

Water parameters

Temperature

22–28°C

pH

6.5 to 8.0

Hardness

5 to 20 dGH

Tank requirements

Minimum volume

300 L

Minimum length

120 cm

Flow

moderate

Lighting

any

Substrate

sand

Driftwood

preferred

Hiding spots

needed

Open swimming room

needed

Feeding

Diet: omnivore, feeds primarily at the mid-bottom.

Carnivore-leaning omnivore. Cichlid pellets (large, high-protein) form the staple diet. Supplement with frozen prawns, frozen mysis, frozen bloodworm (for juveniles), live earthworms, and live feeder shrimp. Larger adults take whole market shrimp, mussel, and fish fillet. Blanched peas and spinach provide fiber. Feed once or twice daily for adults. Juveniles benefit from 2-3 smaller feedings. The green and blue body coloration intensifies on a varied diet with carotenoid-rich foods (shrimp, krill, astaxanthin-enhanced pellets). Avoid feeder fish as a routine food source; they carry disease and parasites and provide poor nutrition compared to prepared foods.

Compatibility

• Genuinely aggressive. The common name is not marketing hyperbole. Males become increasingly territorial as they mature and will dominate a tank of 300 L if not matched with equally assertive tankmates.
• Not a community fish in any conventional sense. Tankmates need to be large, robust, and able to hold their own: other large South American cichlids (oscars, severums, geophagus), large catfish (pleco species, synodontis), and large loaches. Anything small enough to fit in the mouth is food.
• Breeding pairs are significantly more aggressive than single specimens. A male-female pair defending eggs or fry will attack everything in the tank, including fish twice their size. Dedicated species tanks are the safest option for a breeding pair.
• Males reach 25–30 cm and develop a pronounced nuchal hump (forehead bump) with age. Females stay smaller at 15–20 cm. The size difference and the hump make sexing adults relatively easy.

Habitat

Native to Pacific-slope river systems in western Ecuador and northwestern Peru. Found in slow to moderate current over rocky and sandy substrates in warm (22–28°C), slightly acidic to neutral water. The species (Andinoacara rivulatus) was formerly placed in Aequidens and is still sold under that name in some stores. The body is dark green to blue-green with iridescent metallic scales that flash under light. Each scale has a light center and dark edge, creating a reticulated pattern across the body. Fins are edged with bright orange or red, which is the key distinguishing feature from the similar blue acara (Andinoacara pulcher). Males develop a prominent nuchal hump that becomes more pronounced with age and dominance. Adult males reach 25–30 cm in a large tank; females are smaller at 15–20 cm. The species has been in the hobby since at least the 1970s and remains popular with keepers who like large, colorful, behaviorally complex cichlids. Tank-bred stock dominates the trade. Wild-caught specimens still appear occasionally from exporters in Ecuador.

Breeding

Substrate spawner. A pair cleans a flat rock or digs a pit in the sand and the female deposits 200-600 eggs. Both parents guard the clutch fiercely. Aggression toward tankmates reaches its maximum during this period. Eggs hatch in 3-4 days. Fry become free-swimming 4-5 days later and are herded around the tank by both parents. Parental care is extended, lasting 4-8 weeks, sometimes longer if the pair doesn't re-spawn. Fry eat baby brine shrimp and finely crushed pellet from day one. Growth is fast with good feeding. Breeding is not difficult in a dedicated pair tank with a flat stone and stable water conditions. The challenge is the aggression: a breeding pair in a community tank will cause serious damage to tankmates. Pairs bond strongly and may remain together for years, spawning repeatedly. Production per brood is high enough that rehoming or selling juveniles becomes necessary quickly.

Common problems

Aggression management is the primary keeping challenge. A single green terror in a large community with other robust cichlids is manageable. A breeding pair requires planning, space, and an understanding that everything else in the tank will be subordinate. Hole-in-the-head disease (Hexamita) affects green terrors more than many other cichlids, typically manifesting as pits along the lateral line and on the head. The cause is multifactorial: poor water quality, vitamin/mineral deficiency, and chronic stress all contribute. Treatment with metronidazole is effective if caught early. Prevention is a clean tank, varied diet with vegetable matter, and minimal chronic stress. Lateral line erosion (HLLE) overlaps with Hexamita and may have similar causes. Ich in newly acquired fish is treated with standard methods; the species tolerates medication well. Tank size is frequently underestimated; adults need 300 L for a single specimen and 400+ for a pair.

Bioload

Bioload coefficient: 8.0 (large aggressive cichlid; heavy waste).

Bioload coefficients are calibrated against the neon tetra as the anchor (1.0). See the methodology page for the formula and how each value was derived.

Further reading

• Stocking ideas by tank size