Oscar
Astronotus ocellatus
Andinoacara rivulatus
Reviewed for accuracy · Last updated Jan 7, 2026, 12:27 AM
Territorial South American cichlid that becomes highly aggressive when breeding, actively defending territory and dominating tank mates.
Freshwater
Very Aggressive
Medium
66 gal (250 L)
11 in (28 cm)
8–12 years
Omnivore
Resident
Green Terrors are not community fish. They require careful tank mate selection. Choose similarly sized, tough species. Avoid peaceful or small fish.
Large cichlids may coexist with space. Some catfish can be compatible. Territorial disputes are common. Tank layout can reduce conflicts.
Introduce tank mates cautiously. Monitor for bullying. Be prepared to separate fish. Aggression increases during breeding.
Single or pair setups work best. Crowding leads to injuries. Compatibility varies by individual. Experience is recommended.
Green Terrors need ample space to establish territories. A large tank reduces constant aggression. Provide strong filtration for waste control. Stable conditions are essential.
Use sand or fine gravel substrate. Add rocks and driftwood for boundaries. Secure décor to prevent shifting. Plants should be hardy or artificial.
Maintain consistent temperature and pH. Perform regular water changes. Avoid overcrowding at all costs. Observe behavior daily.
These fish are sensitive to poor water. Stress increases aggression. A calm environment improves coloration. Good maintenance ensures longevity.
Green Terrors are omnivorous and opportunistic feeders. They accept pellets, frozen, and live foods. High-protein diets support growth. Quality cichlid pellets should be primary.
Supplement with shrimp and insects. Avoid excessive fatty foods. Feed measured portions daily. Remove leftovers promptly.
Occasional plant matter aids digestion. Vary foods to prevent deficiencies. Juveniles need more frequent feedings. Adults thrive on routine.
Observe appetite and adjust. Overfeeding harms water quality. Balanced diet reduces disease risk. Consistency supports health.
Breeding pairs form strong bonds. They clean spawning sites together. Eggs are laid on flat surfaces. Both parents guard the clutch.
Aggression peaks during spawning. Remove other fish for safety. Eggs hatch within days. Parents protect fry diligently.
Fry become free-swimming quickly. Provide appropriate fry food. Maintain pristine water. Parental care is strong.
Not all pairs are compatible. Breeding requires space and planning. Stress can cause egg loss. Successful breeding is intensive.
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