Get a Huge Tank

Will your fish fit the tank?

Enter the tank, add the fish. Space, load, water and group are judged one at a time, each with its reason, so a pass on one never hides a fail on another. The tank below is a worked example with one fish that does not belong in it.

1 Tank
Brim volume
120 L
Usable water
102 L

Not a rectangle? Work out the volume of other shapes.

2 Stock
FishAdultNumberLoad
Neon TetraParacheirodon innesi3 cm21%
Bronze CorydorasCorydoras aeneus6.5 cm63%
Freshwater AngelfishPterophyllum scalare15 cm105%
OscarAstronotus ocellatus30 cm183%

Common starting points: Black Skirt Tetra, Blue Tang, Bronze Corydoras, Cardinal Tetra, Cherry Barb, Dwarf Gourami.

Side view, to scale
80 cm long, 38 cm high10 cmDrawing 8 of 10 per species

Space

Over

2 Freshwater Angelfish need about 175 L; this tank holds 120 L.

  • Oscar wants a tank at least 150 cm long; this one is 80 cm.
  • Oscar needs about 300 L; this tank holds 120 L.
  • Freshwater Angelfish wants a tank at least 80 cm long; this one is 80 cm.

Load

Over

Stock uses 372% of the waste capacity; Oscar adds 49% of it.

Water

Fits

Shared range: 24 to 26 °C, pH 6.5 to 7.

Group

Over

Neon Tetra with Freshwater Angelfish: Adult angelfish treat neon-sized fish as food once they are big enough, usually within a year.

  • Neon Tetra with Oscar: An oscar eats anything it can fit in its mouth, so tetras become live food.
  • Oscar will eat Bronze Corydoras: at 6.5 cm it is under the 13.5 cm a full-grown Oscar can swallow.
  • Freshwater Angelfish with Oscar: Oscars grow far larger and dig, bully and eat smaller cichlids.
  • Bronze Corydoras is above its minimum school of 6; 8 is better.
  • Freshwater Angelfish defends territory against its own kind; 2 together may fight.

372% of waste capacity (limit 100%)

Loading envelope

0255075100125150010203040Load limit 100%Swim room limit 25%Stocked load, % of waste capacityLongest fish, % of tank lengthPast limit: load and swim room

Load is 372% of capacity (limit 100%). The longest fish is 38% of the tank length (limit 25%). Past limit: load and swim room.

Horizontal: how much of the tank's load the stock uses. Vertical: the longest adult fish as a share of the tank's length. Cross a limit and the point is named in the chart.

How the four checks differ

Space asks whether each adult fish can turn round and whether the tank meets the minimum its species needs. Load adds up how much waste the whole stock makes against what the water volume can carry. Water compares temperature, pH and salinity ranges. Group looks at schooling numbers, temperament and which fish eat or harass others.

Each rule is written out on the method page, and why the inch-per-gallon rule fails is explained in plain terms. Browse all 1,000 fish, check a pair or print a one-page equipment sheet for your stock.