Concrete pond construction - part 1.: "There are many ponds that have only 4 feet of water, but it is generally considered that to really care for large koi then the deeper ponds are really necessary to develop the correct shape for the larger fish. Most of us do tend to overstock our ponds, especially when our earlier small purchases start to grow.
The structure of the pond described here may seem unnecessary in some more sunny parts of the world, but is the standard used by many enthusiasts in South Wales and many koi-keepers in the UK.
It is assumed that you have now decided on the shape and general design for your pond.
The first step is to get a large sheet of graph paper, and draw out the outline of your garden. When this is done you can then start to draw in the outline of your filters and pond. When you are satisfied with this it is a good idea to go out in the garden and follow the steps shown below.
In this photo the pond has been marked out, and the two stepping stones show the rough position of the bottom drains. The upright poles are the basic outline for the filters. It is very important that the filter sizes are also checked at this time as if there is not sufficient room then the size of the pond will have to be reduced to ensure that the surface area of the filters are 33 to 50% of the surface area of the pond. Also check out the space required for items such as vortex chambers etc.
It was relatively easy to mark out this pond as it was all straight lines. If you have curves in the pond walls then the laying out of a hose pipe allows you to experiment with the shape until you get it the way you want.
Digging out of the pond is now well under way. In the right hand corner of the pond can be seen the concrete encased main drain. It had been intended to have the pond raised partly above ground, but as the pond could not be dug any deeper, then it was raised a"