Fish Tank Sizes

Aquarium stocking calculator

Add your tank and your fish to see how full it is, and whether they suit each other.

Your tank
Your fish

    No fish yet. Add the fish you have, or the ones you are thinking of buying.

    Stocking level

    0%

    EmptyFull at 100%150%
    Verdict
    Add some fish
    Temperature that suits everyone
    –
    pH that suits everyone
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      What this checks

      • Whether the tank is big enough for each fish at its adult size.
      • Whether schooling fish have enough of their own kind.
      • Whether there is a temperature and pH that suits every fish in the tank.
      • Whether one fish is likely to eat, nip or bully another.
      • How full the tank is overall.

      How the stocking level is worked out

      For fish under three inches it follows the old rule of thumb of roughly an inch of adult fish per gallon. Bigger fish count for more than their length, because a fish twice as long has several times the body mass, and messy fish like goldfish and plecos count for more again. The model is our own and it is a guide: 100% is a full tank that needs good filtration and regular water changes, not a hard limit.

      Adult sizes, minimum tank sizes, temperatures, pH and group sizes for 100 freshwater species come from Seriously Fish profiles, with goldfish, discus and two plecos filled in from Aquarium Co-Op, Ornamental Fish International and FishBase. Seriously Fish asks for more room than many fishkeepers give, so some common setups get a note about footprint.

      What it cannot tell you

      Individual fish vary, and so do tanks. A heavily planted tank with a strong filter carries more than a bare one. Shrimp and snails are not included yet. Use the result to catch mistakes before you buy, then watch your water tests.