A Guide to Modern Koi Pond Construction

Benching the base

When the walls are completed it is time to think about benching the base.
This is done so that all the fish waste, debris, etc is sucked towards the bottom drains, and so does not lie on the pond bottom or in the corners.

Figure 13a above shows a section through the pond and showing a pond with two bottom drains. Through the centre of the pond a wall about nine inches high has been built across the pond using 18" x 9" x 4" blocks laid so that they are nine inches high.

Figure 13b above shows a plan view of the pond, and in this case it is of a pond say about 15 ft x 10ft with two bottom drains. A wall is built across the centre of the pond nine inches high and four inches wide dividing it in two as shown by the brown colour section. The base is then benched up at the sides of the pond about nine inches sloping down to a minimum layer in way of the bottom drain. This will then create a sort of a saucer effect.

NOTE. There are some that say that with angled deep water returns the base does not need to be benched, but unless you have very efficient returns I would still advise benching.

We can move on and look at rounding the pond corners.