Can Molly Live With Oscar?
Maybe, with caveats. Oscars are predatory cichlids that will eat fish smaller than their mouths, and mollies at 4-5 inches fall into that range.
Why
- Oscars grow to 12-14 inches and need at least 75 gallons as adults. A full-grown oscar sees a molly as a snack.
- Mollies reach 4-5 inches, which fits easily inside an adult oscar's mouth. Size alone makes this pairing risky.
- Temperature overlap of 74-81°F and pH overlap of 7-8 are technically compatible for both species.
- Oscars are messy eaters that will outcompete mollies for food in a shared tank.
- Mollies prefer slightly brackish water, while oscars thrive in pure freshwater. Long-term health implications are unclear.
What could go wrong
An oscar will eventually eat any molly it can fit in its mouth, often within weeks of introducing them.
Gear for a shared tank
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.
Eheim Jager 300W Thermostat Heater
Holds a steady temperature inside the 74-81°F window both species need.
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.
Better pairings to consider
If you want a large cichlid with livebearers, consider a planted 90+ gallon with adult platies already too large to swallow.
Related compatibility questions
Keep reading
Planning a community tank?
Check compatibility for any two freshwater species before you buy. Stop guessing, stop returning fish.
Open the compatibility chart →