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Calculating Pond Stock Rates

21st Nov 2019

We're often asked how many fish is safe to keep in a pond - the answer it usually less than you think and over stocking is a common problem. There's a relatively simple way to work out how many fish you should keep in your pond to make sure your fish and healthy. 

Why does it matter?

As well as the build up of ammonia, over-crowding your pond can lead to oxygen depletion and put a strain on the filtration system. There are many factors that can be taken into account when calculating the stock rates for your pond; adequate aeration, filtration and even planting and time of year affect the amount of fish which your pond may support.The simplest method is to use the surface area of the pond as a guide. Oxygen enters the pond through the surface, so the larger the surface area, the more oxygen in the water and so the greater the quantity of fish the pond can support.

How many fish can I have?

As a general rule, a pond with a surface area of 9m2 will support a total of 5 metres of adult fish (it is important to take into account the fact that the fish may grow and will require more oxygen).The surface area is the length of the pond in metres multiplied by its width. If the pond is an irregular you should use an average length and width measurement.

The formula for calculating stock rates is; Max. Stock = ((L x W) ÷ 9) x 5 E.g. a pond is 5 metres long, 3 metres wide;

Max. Stock = ((L x W) ÷ 9) x 5

= ((5 x 3) ÷ 9) x 5

= (15 ÷ 9) x 5

= 1.7 x 5

= 8.3 metres of fish. Therefore, the pond can support 8.3 metres of fully grown fish. It is important to remember that this rule is just a general guideline as there are many factors to take into account to give a definite maximum stock rate for a given pond.