How large is an oscar when it starts eating shrimp?

Oscars begin hunting small tankmates around 3-4 inches. Cherry shrimp are vulnerable from the day they are added to the tank, even to juvenile oscars.

Will a single small oscar eventually eat all the shrimp?

Yes. One 4-inch oscar will clear out a shrimp colony faster than a full-sized one. The fish does not need to be mature to be a predator.

Can I add lots of hiding places for shrimp?

Hiding places slow but do not prevent predation. Oscars are persistent and will work through any structure in the tank over time. The shrimp will not survive long-term.

Can Cherry Shrimp Live With Oscar?

By Alex WalshLast reviewed Apr 18, 2026

No, oscars eat cherry shrimp. An adult oscar reaches 12-14 inches and has a wide mouth that can swallow adult shrimp in one bite.

Why

Oscars are large cichlids that grow to 12-14 inches. Their mouths are built to take bites out of tankmates. Cherry shrimp fit entirely inside the average oscar jaw.
Oscars are predatory by nature. Even if they do not swallow every shrimp immediately, they will pick through the tank and eliminate the population over weeks.
Cherry shrimp hide on surfaces, plants, and substrate. Oscars sift through all of these areas while rooting for food.
Temperature overlap 74-80F covers both species, and pH 6.5-8 is wide, but parameter overlap does not resolve predation.
Shrimp colonies in an oscar tank never establish. Any surviving shrimp stay hidden permanently and stop breeding.

Minimum shared tank

75 gallons

Shared temperature range

74-80°F

What could go wrong

The shrimp population vanishes over 4-6 weeks. Oscars may ignore dead shrimp, but they will root out every live one eventually.

If you keep them in separate tanks

Sized for the 75 gallon minimum this pairing needs. Affiliate links — we earn a small commission if you buy through them.

Fluval 307 Performance Canister Filter

Oversized filtration is what lets you stock two species together without water quality crashing. Rated for a tank slightly larger than the 75 gallon minimum.

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Eheim Jager 300W Thermostat Heater

Holds a steady temperature inside the 74-80°F window both species need.

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API Freshwater Master Test Kit

Keep ammonia, nitrite, and nitrate in check. Two-species tanks have more bioload and less margin for error than single-species setups.

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Better pairings to consider

Oscars are best kept species-only or with other large cichlids like convicts or salvini. Cherry shrimp thrive with small peaceful community fish like otocinclus, corydoras, or rasboras.