How to Measure the Volume of your Aquarium

You need to know the volume of your aquarium when adding medication or chemicals to the water. You also need that figure to work out the optimum number of fish your tank can hold or replace a given percentage of water in the aquarium.

Volume is defined as the amount of space taken up by three-dimensional object, and often refers to liquid volume—which is the amount of space taken up by a liquid filling a container.

The US customary units for measuring volume are cups, pints, quarts and gallons. The British metric system units are milliliters and liters. A large amount of liquid, such as that in most aquariums, is usually measured in gallons.

To Calculate the Volume of a Rectangular Fish Tank

It may be easier to work in inches as many tanks are built to “inches-and-feet” dimensions. Measure the length, height and depth of the tank, multiply the figures, and multiply again by 0.00433 (to convert cubic inches to gallons).

For the length, measure the front or back panel of your aquarium, from left to right. For purposes of illustration, let’s assume that it measures 18 inches.

For the height, measure the aquarium from top to bottom. (Let’s say it measure 12 inches).

For the depth, measure the side of the aquarium, from front to back. (Again, it measures 12 inches).

Volume of the tank = Length x Height x Depth x 0.00433

First, multiply the three measurements taken:-

• Measure: 18(L) x 12(H) x 12(D) = 2592 cubic inches

Then multiply this number by 0.00433.

• Result: The volume of the tank is approximately 11.2 gallons

For a more accurate measurement, you should measure the insides of the aquarium instead. There should be a slight reduction in its volume if you do this.

How Much is 20% of your Aquarium’s Water?

For example, if you have a 10-gallon aquarium:-

• 20 per cent of 10 gallons = 0.20 x 10 gallons = 2 gallons

To convert gallons into cups, multiply by 16. Thus,

• 2 gallons x 16 = 32 cups

1 cup ≈ 250 mil (8 oz)
1 liter ≈ 35 fl oz or 4 cups
1 gallon ≈ 4 liters or 16 cups

So when you need to replace 20 per cent of your 10-gallon aquarium’s water, use a clean measuring cup to remove 32 cups of water from the tank. Now, mark the new water level on the outside of your aquarium with a marker. When making future water changes, you can simply drain the water in the aquarium down to the mark and replace it with fresh water.

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