TankStocking

How many fish in a 30 gallon tank?

A 30-gallon (114 L) tank is a true community aquarium — room for multiple groups, a centrepiece fish, and real stability.

Thirty gallons is where the hobby opens up. You can run a full mid-water school, a bottom group, and a centrepiece species together, with enough water volume to keep parameters stable. Taller 30-gallon tanks also suit fish like angelfish and gouramis that appreciate height.

Rule of thumb for a 30-gallon (114 L) tank: a full school of 10–12, a bottom group of 6–8, and one or two centrepiece fish — chosen so nothing can eat or bully anything else. Use the planner below — it's pre-set to 30 gallons — to test your exact list against minimum-tank, schooling, temperature, aggression and bio-load checks.

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      Stocking ideas for a 30-gallon tank

      Each idea below is scored by the same engine as the planner — tap one to load it.

      Full planted community

      ✓ Good starter plan

      6× Boesemani Rainbowfish, 8× Bronze Corydoras, 1× Honey Gourami

      A rainbow school, a cory shoal and a gentle centrepiece — a complete, lively 30-gallon.

      Load this build in the planner ↑

      Dwarf cichlid display

      ✓ Good starter plan

      2× German Blue Ram, 12× Cardinal Tetra, 6× Sterbai Corydoras

      A ram pair, a cardinal school and warm-water Sterbai cories — warm, soft, planted, and full of colour.

      Load this build in the planner ↑

      How many of each popular fish fit a 30-gallon tank?

      The honest, engine-derived answer instead of a single guess: comfortable single-species display counts for popular community fish at this size. Each number is deliberately conservative — it leaves headroom for water-quality swings and tankmates, so it is a comfortable target, not a hard ceiling. Tap a count to load that fish in the planner.

      Comfortable display numbers for a 30-gallon tank — single-species, leaving room for tankmates
      SpeciesAdult sizeComfortable count (this tank)
      Neon Tetra 3 cm ~18
      Cardinal Tetra 3 cm ~18
      Ember Tetra 2 cm ~20
      Harlequin Rasbora 4.5 cm ~17
      Zebra Danio 5 cm ~13
      Cherry Barb 5 cm ~16
      Guppy (Fancy) 5 cm ~16
      Platy 6 cm ~15
      Molly (Common / Sailfin) 12 cm ~6
      Bronze Corydoras 7 cm ~12
      Kuhli Loach 9 cm ~13
      Cherry Shrimp 3 cm ~18

      Good to know

      What is the maximum number of fish for a 30-gallon tank?

      There is no single number — it depends on the adult size, waste output, and social needs of the species. The planner above estimates a stocking level for your exact list rather than guessing from gallons alone.

      Can I use the "one inch of fish per gallon" rule?

      It is a rough starting point at best and breaks down quickly: a 3-inch goldfish produces far more waste than three 1-inch tetras, and the rule ignores schooling needs, aggression, and adult size. TankStocking weights bio-load by body size and waste class and applies hard welfare checks instead.

      Should I add all the fish at once?

      No. Cycle the tank first, then add fish in small batches over several weeks so the biological filter can keep up. A fully-stocked plan is the destination, not the starting point.

      Plan a 30-gallon tank

      Related guides on TankStocking — each scored by the same welfare engine as the planner.

      Single-species stocking in a 30-gallon tank

      Tank-mate guides for these fish

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      Stocking levels are planning estimates, not guarantees — individual fish, filtration, planting, and maintenance all matter. Cycle the tank before adding livestock and verify your own water. How TankStocking works →