The more you talk to different people in this Koi Hobby .. then the more different and confusing answers you will get ... Ask about building a pond and you will receive all sorts of strange and wonderful different methods ... and the same thing applies to the answers you will receive if you ask someone about the pond that you are proposing to build and you ask them how many gallons of water it will hold and what size pump do you need on that system for it work efficiently ... So here below we are going to try to set the record straight and provide you with information that will stand you in good stead for the rest of your pond keeping days .. and of course we hope that will be a long - long time ...

While these formulas may at first seem a little complicated, if you follow them slowly step by step you will begin to understand what is required and be well on your way to understanding what sort of environment you need to create a good environment for your Koi and other pond life.

1. To calculate your pond volume: Length x Width x Average Depth x 6.23 = Approx. Gallons in pond.

To calculate the EFFECTIVE and EFFICIENT volumes of your pond.

Then the following factors must also be considered when trying to estimate your pump and filter sizes that you will require...

a). For an average pond water depth of less than 2 1/2 feet then increase by 25%

So if you have a pond that holds 1,000 gallons then by adding this 25% you have then to look for a filter and a pump that would cope with 1,250 gallons ...

For this purpose will we assume that you have a circular pond of say 15ft diameter .. OK .. so half of this circumference is the Radius which in this case is 5.5ft - So we take that 7.5ft and multiply it by itself 7.5ft which will give us 56.25 - multiply this by 22 = 1237.5 - then divide this by 7 and we have a figure of 176.78 which we then multiply by the average depth of the pond .. and in this case we will say that it is 4ft - so the figure we then should have is 707 - then we multiply this by that magic formula 6.23 and we end up with a figure of 4405 gallons - divide that by 220 and you have the volume of your pond in tons which in this case would be 20 tons ...

Take a piece of string and lay it round the perimeter of your pond .. then measure that piece of string to see how long it is .. in this example we shall say we end up with our string having a length of 80 ft ...

So lets take that 80 ft and divide that by 4 = 20ft - multiply that by itself, i.e. 20 x 20 and this will give you 400 and that is your surface area ... next we multiply that by the depth - lets say 4ft again and we then have a figure of 1,600 which we then multiply by that magic formula 6.23 to end up with 9,968 gallons - divide by 220 to give us the total tons and we have 45 tons ..

b). If however the pond is located in full sun then increase that figure again by a further 25%, or if there is only half day full sun increase by that original figure by another 17.5% - thus if we have a pond with 1,000 gallons which is less than 2 1/2 feet deep and we have already added 25% to cope with this - and it is in full sun all day then we need to add another 25% so if we take the original figure of 1,000 gallons then it was increased to 1,200 gallons then we add a further 25% which would then give us a total of 1,562 gallons and need a filter and a pump that will cope with that ... and instead of adding that additional 25% as we did for a pond in full sun .. if it is half day sun then the figure is less and only 17.5% needs to be added .... But please remember that you cannot over filter a pond and it is better to be over with your estimates than it is to be under ....

That is a question we are very frequently asked .. so let's try and equate it so that we can all understand ...

Remember even small fish need plenty of room to move and to exercise ... the more room they have then the happier and healthier they will be .. do not overcrowd .. it can be fatal ...

a). So If the total “fish length” in your pond is more than 8 inches for every 250 gallons then an extra percentage must be allowed. For example if a pond of 500 gallons was capable of containing 16 inches of fish, but if the actual stocking level was 32 inches then you would need to increase the size of your filter by another 50% – this means that both the filter and pump must be able to cope as though the pond has 750 gallons and not the 500 gallons. Another example: You have a pond with say 1000 gallons and it is 2 ft. deep, and in full sun, and you have 64 inches of fish.

Then apply this formula: 1000 gals+ 25% for Depth =1250gallons, + 25% for Full Sun=1500, + 50% for the 64 inches of fish you have =1,877 gallons