Enter the total number of fish and the total volume (liters) into the Calculator. The calculator will evaluate the Fish Per Liter. 

Fish Per Liter Formula

FPL = F / V


  • FPL is the Fish Per Liter (fish/L)
  • F is the total number of fish
  • V is the total volume (liters)

To calculate Fish Per Liter, divide the number of fish by the total volume in liters.

How to Calculate Fish Per Liter?

The following steps outline how to calculate the Fish Per Liter.

  1. First, determine the total number of fish. 
  2. Next, determine the total volume (liters). 
  3. Next, gather the formula from above = FPL = F / V.
  4. Finally, calculate the Fish Per Liter.
  5. After inserting the variables and calculating the result, check your answer with the calculator above.

Example Problem : 

Use the following variables as an example problem to test your knowledge.

total number of fish = 200

total volume (liters) = 1000

Frequently Asked Questions

What is the ideal Fish Per Liter ratio for a healthy aquarium?

The ideal Fish Per Liter (FPL) ratio depends on the species of fish and their size. Generally, a lower density, such as one small fish per 2-3 liters, is recommended for most community aquariums to ensure a healthy environment.

Can the Fish Per Liter formula be used for any type of aquarium?

Yes, the Fish Per Liter formula can be applied to both freshwater and saltwater aquariums. However, the specific needs and space requirements of the fish species should always be considered.

How does the volume of decorations and substrate affect the Fish Per Liter calculation?

Decorations and substrate displace water in an aquarium, effectively reducing the total volume available for fish. Therefore, when calculating Fish Per Liter, it’s important to consider the actual water volume, which may be less than the tank’s nominal volume.

Is there a maximum Fish Per Liter ratio that should not be exceeded?

While there’s no universal maximum FPL ratio, it’s crucial to avoid overstocking. Overcrowded tanks can lead to poor water quality, stress, and health problems for the fish. As a general guideline, err on the side of fewer fish per liter to ensure a healthier aquarium environment.