Enter the total length, width, and height of livable water of your aquarium into the fish stock calculator to determine the amount of fish that can live in the aquarium.

Fish Stock Formula

The following formula is used to calculate how much fish to stock an aquarium with.

"F = L*W*H*.004329*2
  • Where “F is the inches of fish
  • L is the length of livable water (in)
  • W is the width of livable water (in)
  • H is the height of livable water (in)

Aquarium Stock Definition

What is aquarium stock? An aquarium stock is an amount of fish that someone should place in any given aquarium to allow for proper living space for fish. In general, this is usually provided as 2 inches of fish per gallon of water. This assumes proper filtration and care of the fish and aquarium.


How to calculate how much fish i can have in an aquarium?

  1. First, determine the length of water.

    For this problem, the length of the aquarium is 10″.

  2. Next, determine the width.

    In this example, the width is 12″.

  3. Next, determine the height.

    Importantly, this should be the height of livable water. Do not include stones or air space in this height. In this example, the height is 10″.

  4. Finally, calculate the fish stock.

    Using the formula, we find that we should stock this aquarium with (10*12*10)*.004329*2 = 10.389″ or rounding down, approximately 10 inches of fish. That could be 1 – 10 inch fish or 2 – 5 inch fishes etc.

aquarium stock calculator
fish stock formula