Fish Compatibility Checker
Select two species to check if they can safely share a tank.
This tool is for informational and educational purposes only. It is not a substitute for professional financial, medical, legal, or engineering advice. See Terms of Service.
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Request a ToolHow to Use the Fish Compatibility Checker
Select two fish species from the dropdowns to instantly see whether they can live together safely. The result shows one of three levels:
- Compatible: These species generally coexist peacefully in a properly sized tank with appropriate water parameters.
- Use Caution: These species can sometimes coexist, but there are risk factors such as fin nipping, size differences, or occasional aggression. Additional notes explain what to watch for.
- Incompatible: These species should not be housed together due to predation risk, aggression, or incompatible water temperature requirements.
The result includes species-specific notes explaining the reason for the rating. Use Share to send the result to a fellow hobbyist, or Copy to save it to your notes before a trip to the fish store.
About Fish Compatibility
Freshwater fish compatibility depends on three main factors: temperament, size, and water parameters. A peaceful community fish like a neon tetra can be kept with most other peaceful species of similar size, while an aggressive predator like an Oscar will eat or harass nearly anything smaller than itself. Temperature is a hard constraint: goldfish need cool water (65-72°F) while tropical fish need warm water (74-82°F), making them incompatible regardless of temperament.
This checker covers 12 of the most commonly kept freshwater species. For species not in the list, research the individual species' temperament, adult size, water temperature needs, and feeding behavior before combining them. A general rule: if you are unsure, start with a quarantine tank to observe interactions before adding new fish to an established community.
Frequently Asked Questions
Can a betta fish live with other fish?
Male betta fish are highly territorial toward other bettas and similar-looking fish, but can coexist with many peaceful community fish in a tank of at least 10 gallons. Good betta tank mates include corydoras catfish, harlequin rasboras, mollies, and mystery snails. Avoid fin-nipping species like tiger barbs, other bettas, and fish with large flowing fins that the betta may mistake for a rival. Female bettas are generally less aggressive and can sometimes be kept together in larger groups called sororities.
Can goldfish live with tropical fish?
Goldfish and tropical fish should not be kept together. Goldfish are cold-water fish that thrive at 65-72°F, while most tropical fish require 74-82°F. Keeping goldfish at tropical temperatures stresses them and shortens their lifespan significantly. Additionally, goldfish are messy fish that produce a large amount of ammonia, and they will eat smaller fish and invertebrates. Goldfish do best in a species-only tank or with other cold-water fish like white cloud mountain minnows.
What fish can live with oscars?
Oscars are large, aggressive cichlids that will eat any fish small enough to fit in their mouth. Suitable tank mates must be large, robust fish that can hold their own. Options include other large cichlids like Jack Dempseys, Jaguar cichlids, and convicts (in large tanks), as well as large plecos and large catfish. A single oscar requires at least a 55-gallon tank; pairs need 100+ gallons. Most hobbyists keep oscars alone or in species-only setups for this reason.
Why do tiger barbs nip fins?
Tiger barbs are naturally active schooling fish that establish a pecking order through fin nipping. When kept in groups of 6 or more, they direct this behavior mostly at each other. When kept in smaller groups or alone, they focus their nipping on other fish, especially slow-moving species with long flowing fins like bettas, angelfish, and fancy guppies. If you want to keep tiger barbs in a community tank, keep at least 8-10 together and avoid pairing them with fin-nipping targets.