Calculate the pond volume to determine the correct filter for your pond

To calculate the volume of a circular pond we need to know the radius of the circular cross-section of the pond - this is the measurement from the centre of the circle, to the outer-edge.

Here is the basic sum:

Volume = radius² x 22 ÷ 7 x depth = m³ = x 1000 = litres


e.g. 1.5² x 22 ÷ 7 x 0.75m = 5.3m³ = 5300 litres
e.g. 5ft² x 22 ÷ 7 x 2ft = 157ft³ = 978 gallons

Click here to calculate a Circular pond

To calculate the volume of a rectangular pond we need to know the Length, Width, Depth.

Here is the basic sum:

Volume = Length x Width x Depth.

e.g. 3m x 2m 0.75m = 4.5m³ = 4500 litres
e.g 10ft x 6ft x 2ft = 120ft³ = 747 gallons

Click here for the Rectangular pond calculator

NOTE: Additional factors that may require adjustment to the above figures

1. Pond Depth – If your pond is less than 75cm or 2 ½ feet deep it will heat up and cool down quicker than a deeper pond, so add 25% on to the original calculated pond volume.

2. Location – If your pond is subject direct sunlight all day it will get hotter than a pond that has the benefit of partial shade for a few hours a day, so add 25% on to the original calculated pond volume. For example; 10,000 litre pond + 25% (2500l) for shallow water + 25% (2500l) for direct sunlight = 15000 litres.

3. Fish Stocking levels – Oase filter selection charts are based on maximum fish stock as follows:-
Average fish pond (e.g. gold fish) 1 kg of fish per 1000 litres of pond water
e.g. a 4000 litre pond will support up to 4 kgs of fish (with a Biosmart Set 2B Filter Set)
Koi pond allows for 3 kg of fish per 1000 litres of pond water
e.g. a 4000 litre pond will support up to 12 kgs of Koi (with a Biosmart Set 2D Filter Set)
These are maximum recommended stocking levels, so if you have higher levels of fish stock in your pond, you should consider reducing your stock or increasing your pond volume. Remember fish, like people, need space to enjoy a healthy life style. Serious overcrowding can be fatal.

If in doubt, please e-mail us with your questions or call us on 02392 373735 for free, expert advice.