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Oscar

By The Aquarium Calculators Editorial Team ·

Astronotus ocellatus

Complete Oscar care guide covering carnivore diet requirements, aggressive temperament, minimum 55 Gallons tank setup, and compatible freshwater tankmates. Difficulty: Advanced.

Oscar

Quick Answer

Oscar (Astronotus ocellatus) is a captivating and highly sought-after freshwater species. It requires a minimum 55 Gallons aquarium with a pH of 6.5 - 7.5 and temperature range of 22-26°C. As a carnivore with aggressive tendencies, careful tankmate selection is essential.

Intro

Oscar (Astronotus ocellatus) is a captivating and highly sought-after freshwater species. Known for their aggressive nature and distinct appearance, they occupy the middle levels of the aquarium and bring dynamic energy to any setup.

Setup

Oscar requires a stable, well-filtered aquarium of at least 55 gallons. They thrive best with moderate water movement and a reliable heater to maintain temperatures around 22-26°C. Ensure pH levels remain consistent between 6.5 - 7.5 to prevent stress and support long-term health.

Feeding

As a carnivore, the Oscar is not a picky eater. They should be fed a high-quality base of flakes, sinking pellets, or wafers. Periodic supplementation with frozen or live foods, such as bloodworms or brine shrimp, will boost their health and colors.

Compatibility

Oscar has a aggressive temperament. They are compatible with other fish of similar sizes and temperaments. Avoid placing them with aggressive species or tankmates they are listed as incompatible with, such as: neon tetra, cardinal tetra, guppy, corydoras, molly, platy, ember tetra.

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Tank Position
Middle
Water Temp
22-26°C
Adult Size
See profile
Water pH
6.5 - 7.5

Species Characteristics

Adult Size
Lifespan
Growth Rate
moderate
Tank Compatibility
Community compatible
Indoor Aquarium
Yes

Water Parameters

Water Temperature
Humidity
Water pH

Tank Lighting

Tank Lighting
Standard lighting
Light Hours
N/A
Intensity
moderate

Feeding & Diet

Diet Type
Diet: Carnivore
Feeding Schedule
N/A
Live Food Options
N/A

Continue Learning

Recommended Tools

Fish Compatibility Calculator fish compatibility

Health & Disease

Ich (White Spot Disease) common disease • all fish

Related Guides

Understanding pH in Aquariums water parameters • ph

Similar Species

African Butterflyfish Care Guide: Tank Size & Diet semanticSimilarity African Cichlid Care Guide: Tank Size & Tank Mates semanticSimilarity Bala Shark Care Guide: Tank Size & Tank Mates semanticSimilarity

Frequently Asked Questions

How many Oscar Cichlids should be kept together?
Keep a single specimen or a matched pair in a tank of at least 75 gallons (284 liters) for one fish, 125+ gallons (473 liters) for a pair. Oscars (Astronotus ocellatus) grow up to 12-14 inches (30-35 cm) and require huge aquariums with robust filtration systems. Two juveniles in under 100 gallons will fight to severe injury as they mature. A bonded pair needs 125+ gallons with multiple visual barriers. For a single fish, 75 gallons minimum with footprint of 48x18 inches (120x45 cm). Avoid with smaller fish (under 4 inches) as they will be eaten.
What are the exact water parameters for Oscar Cichlids?
Target pH 6.5 - 7.5, General Hardness 5 - 15 dGH, Carbonate Hardness 4 - 12 dKH, Total Dissolved Solids 150 - 400 ppm, Electrical Conductivity 300 - 800 μS/cm, and temperature 74°F - 80°F (23°C - 27°C). They produce massive waste; maintain strict water cleanliness with nitrates below 20 ppm (ideally <10 ppm) using weekly 40% water changes. Use a canister filter rated for 3x tank volume (100+ gallons of filtration). Ammonia must be 0 ppm; they are prone to Hole-in-the-Head disease in dirty water. Provide strong aeration.
What is the dietary and medication protocol for Oscar Cichlids?
They are large carnivores requiring 50% protein, 15% fat, 35% plant matter. Feed premium large cichlid pellets (Hikari Gold, New Life Spectrum), freeze-dried krill, crickets, earthworms, and frozen silversides twice daily. Offer blanched peas and spirulina wafers weekly. Avoid fatty foods (beef heart) which cause bloat. Medication alert: Tolerate copper (0.2 mg/L) and formalin. Praziquantel is safe. Salt baths up to 5 ppt treat external parasites. Quarantine with metronidazole (5 mg/L) for 10 days to treat hexamita.
How to breed Oscar Cichlids with environmental triggers?
Condition a bonded pair with live earthworms and krill for 4 weeks. Raise temperature to 80°F (27°C) and perform 30% water change with slightly cooler (72°F/22°C) water. Provide a flat slate or large river rock. The pair cleans the site; female lays 1,000-3,000 eggs. Both parents guard and fan eggs. Eggs hatch in 72-96 hours at 78°F (25.5°C). Wrigglers become free-swimming in 7-10 days. Feed crushed flakes, baby brine shrimp, and microworms. Parents are good caregivers but may eat fry if stressed. Frequent 30% water changes are critical.

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