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    FRESHWATER AQUARIUM PLANNING

    Fish Compatibility Chart & Checker

    Can these fish share an aquarium? Compare two freshwater fish and explore important differences in water needs, behavior, and tank setup before you make a stocking decision.

    30 freshwater fishQuick side-by-side checksInteractive comparison chart


    THE CHECKER

    Which fish would you like to compare?

    Choose a pair to view potential concerns and a simple water-condition comparison.

    Step 1 of 2



    Try an example:
    Add your tank details Optional — for more specific checks







    Leave unknown measurements blank. Tank size, fish counts and sex matter, but cannot by themselves establish a safe match.

    Your comparison will appear here

    Select two fish, then tap Check compatibility to review the findings.

    FISHKEEPING GUIDE

    What makes two aquarium fish compatible?

    Fish compatibility is about more than finding species that can survive at the same temperature. A good freshwater community also needs compatible temperaments, enough swimming or territorial space, suitable water chemistry, and appropriate social groups. This checker helps you spot issues worth investigating before fish are introduced.

    01

    Temperature & water

    Compare temperature, pH and general hardness (GH). Published care ranges can describe different kinds of tolerance, so an overlapping number is only a starting point.

    02

    Behavior & tank mates

    Territorial fish, fin-nippers and predators may cause problems even when water requirements overlap. The size and life stage of each fish can change the risk.

    03

    Tank size & social needs

    Consider adult body size, swimming room, hiding places, fish numbers and whether a species needs a proper school or group. Water volume alone cannot answer these questions.

    Fish compatibility questions

    How do I use a fish compatibility checker?

    Select your first and second fish. If you know them, add tank temperature, pH, GH, tank dimensions and fish counts. Check the highlighted concerns, compare the water ranges, and investigate the remaining care requirements before making a stocking decision.

    Does matching pH and temperature mean two fish can live together?

    No. A shared water range does not eliminate aggression, stress, fin-nipping, predation or differences in activity. Tank footprint, hiding places, adult size and group requirements also affect the outcome.

    Why does the chart say more research is needed?

    Some pairs do not have enough independently checked, species-specific evidence for a reliable conclusion. No warning found is not proof that a combination is safe. The tool deliberately shows those gaps instead of guessing.

    Is the compatibility chart suitable for a planted community aquarium?

    It can help identify initial questions, but a planted aquarium still needs suitable territory, open swimming space, group sizes, filtration and stable water. Plants and decorations do not automatically prevent territorial or predatory behavior.

    Can I compare two fish of the same species?

    Yes. Select the same fish twice, then add known sex and group information under tank details. Same-species aggression and social requirements may be important, and not all species have the same group or sex needs.