aquanerd

Aquarium Stocking Calculator

How many fish can your tank actually hold? Pick a tank size and your livestock to see your stocking level and catch compatibility problems before you buy.

New here? Start from an example

1. Your tank size

2. Add livestock

  • Cherry ShrimpPeaceful · 1.2"
    0
  • Amano ShrimpPeaceful · 2"
    0
  • Nerite SnailPeaceful · 1"
    0
  • Mystery SnailPeaceful · 2"
    0
  • Chili RasboraPeaceful · 0.7"
    0
  • Neon TetraPeaceful · 1.2"
    0
  • Ember TetraPeaceful · 0.8"
    0
  • GuppyPeaceful · 1.5"
    0
  • PlatyPeaceful · 2.5"
    0
  • MollyPeaceful · 4"
    0
  • Zebra DanioSemi-aggressive · 2"
    0
  • Corydoras CatfishPeaceful · 2.5"
    0
  • Kuhli LoachPeaceful · 3.5"
    0
  • Dwarf GouramiSemi-aggressive · 3.5"
    0
  • Betta (male)Territorial · 2.5"
    0
  • Pea PufferPredator · 1"
    0
  • AngelfishSemi-aggressive · 6"
    0
  • Bristlenose PlecoPeaceful · 5"
    0
  • Fancy GoldfishPeaceful · 8"
    0

Stocking level

0%

20-gallon tank · estimate, not an exact science

Tips

  • •Add a tank size and some species to see your stocking level.

Cycle the tank first and stock slowly. Need the gear too? Build a full kit →

How it works

  1. 1

    Pick your tank size

    From a 5-gallon nano to a 75-gallon community tank.

  2. 2

    Add your fish

    Choose species and quantities. We track bioload, minimum tank size, group needs, and temperament.

  3. 3

    Read the result

    A live stocking percentage plus warnings — overstocking, incompatible species, schooling fish kept in too-small groups.

Methodology & sources

How the percentage is calculated. Each species carries a bioload value — roughly the gallons it needs, scaled from adult size and waste output. We sum those across your stock and divide by your tank volume: stocking % = Σ(qty × gallons-per-fish) ÷ tank gallons. That is a refined version of the old “inch per gallon” rule of thumb — handy for planning, but it does not model your filtration or surface area the way a dedicated tool like AqAdvisor does.

What’s grounded vs. what’s our estimate. Each species’ care parameters — minimum tank size, schooling group size, temperament, temperature needs — are cross-checked against published profiles (Seriously Fish for the fish; Aquarium Co-Op for shrimp, snails, and goldfish); the per-species sources are listed below. Two honest caveats: our minimum tank sizes are practical hobby floors and can be more permissive than a source’s ideal (Seriously Fish suggests ~41 L for a single betta; we flag 5 gallons as the floor), and the single stocking percentage is our own heuristic — read it as a band (comfortable / near capacity / overstocked), not a precise score.

Not a replacement for the basics. Cycle the tank before adding livestock, test for ammonia, nitrite, and nitrate, and stock slowly. No calculator overrides what your test kit tells you about your own water.

This is a planning tool maintained by the aquanerd Editorial team — it is not reviewed by a named ichthyologist, and the numbers are deliberately conservative estimates rather than measured values. For authoritative, species-level care parameters, cross-check trusted references: Seriously Fish, Aquarium Co-Op, AqAdvisor.

Per-species care sources (19)