For most potential pondkeepers the biggest single dilemma in planning a pond and building a pond, how big do i make it? 

Whatever size of your pond you had in mind , double it!!.

For most pondowners wish 12 months down the line they had made it bigger.

Opposition to how much room it will take up and the cost of the project limit the end result in many cases. Only when the fish start growing do you wish it was bigger.

Factors to take into account when deciding the size of your pond.

Weather/Climate

If you live in a area where you get cold winters with permanent ice like the NE United States , Canada or Northern Europe , your pond should be a minimum of 2 feet or 60cm deep. Deeper the better if you can.

In warmer climates where ice is not a issue , evaporation is. 

Why?

To stop your pond freezing solid therefore killing off your fish and to allow a thermocline, this is a section of water in the bottom of the pond that is slightly warmer due to no wind chill and been insulated by the surronding rock/soil etc.

This is why you see fish sit in the bottom of the pond to utilise this in low temperatures.

Another factor is the more water you have the more stable the temperature, like a ocean which takes weeks to change temperature. This keeps any shock and stress to your fish and plants to a minimum.

Warmer Climates make the pond heat up to quickly or stressing the fish and suffering from high evaporation.

Type of fish

Most people put in a pond to keep fish , decide on what fish type you are going to place in the pond Koi or goldfish. 

Koi 

Known as the 'pigs of the pond' for good reason , they love to root around stirring up gravel and marginal baskets if you have allowed them access that is. Koi are fast growers and your pond size should be 50% bigger than if you were keeping just goldfish. Most of this extra size should be in depth. This enables the koi to grow correctly using all the muscles in it's body. A long thin fish can be the result of a koi constantly swimming in shallow water, this is caused by the fish never swimming down using a different set of muscles.

Goldfish

Goldfish or goldfish family (Carraus Aureatus) are very hardy and are certainly easy to keep. A pond size is not as demanding , but a good part of it should be at least 18 inches deep to allow refuge from predators and harsh winters , remember a simple saying to depth , furthur north furthur down.

How do i calculate the size of a pond.

A easy formula to remember.

For Imperial Gallons

Length x Times x Breadth x 6.23. To then get litres if required times by 4.54.

For a oval shaped pond

1/2 dia x 1/2dia x depth x 3.14 x 6.23. 

For US Gallons

Length x Times x Breadth x 7.48 .

For a oval shape pond

1/2 dia x 1/2 dia x depth x 3.14 x 7.48

The easiest and most reliable method to get the exact gallonage is to connect your hosepipe to a water meter when you initally fill it up. Ask your local retailer some either sell , borrow or rent them. Knowing your exact gallonage is very important when it comes to adding chemicals at a later date.  

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