The basic principles
Making a garden pool involves deciding whether to buy a rigid pool or use a liner. If you purchase a rigid, fibreglass pool you are making life easy in one way, but you are committing yourself to a pool of a set shape and size. You would need to ensure that the ground is dug to the exact depth of the pool and is dug to the correct shape. You can dig to a shape, but it may involve some filling in around the sides after the fibreglass pool is put in place. The soil should be firmly tamped down to make the pool secure.
If you build a pool with a butyl liner you have more opportunity to decide the shape. However, you must be aware that butyl can be pierced by gravel or larger stones in the soil. Therefore you must ensure that the soil is carefully excavared. You must dig it to a slightly greater depth than you will need for the pool and take out all stones. This can be a painstaking job. Then you will lay sand thickly over the surface and press it down.After the sand has been laid the pool should be at the depth that you want.
If you want a pool of varying depths, possibly for water plants, you can dig it in steps. However, it is vital to realize that you must work out the exact surface area of ground to be covered and then purchase a liner twice the size needed. The calculation should include the area of the pond walls as well as the bottom. The liner should stretch over the side and lie on the ground to prevent it slipping. It can be covered with soil or edging stones to hold it down.
It is possible to have a rigid edge, like the pool in the picture, but some pool owners have a boggy edge at one side to allow for a bog garden, which might incluide such plants as cranberry and insectivorous plants, such as sundew.
However, as a liner might be covering the soil near the edge , it is often a good idea to have a container garden surrounding the pool. Large pots will contain the range of flowers that you want.To plant water flowers, have them in piots then lower them into the water at the depth that you want.
Safety is paramount. If you have children or if children can obtain access, think twice about a pool. A protective fence is always a good idea, and the containers will help to provide extra safety. However, no children should be unsupervised near a pool; and the safety of vulnerable adults must also be considered. Netting is also important, and you should carefully consider putting a well secured safety net across the pool.
This brings us to electricity. The water will need renewing every so often, so you will need a pump. Water and electricity do not mix, so unless you are a trained electrician, do not wire the pump up yourself. Bring in a qualified electrician; and the services of a plumber are to be considered when connecting up the water supply. Take no risks.
The pool will need to be kept clean, especially as autumn leaves will get into it and clog up the bottom. An annual cleaning is needed. You can put the mud debris from the bottom of the compost heap or in the leaf mould bin.
Fish are a great addition to a pond, but they need to have clean water, so you will need to refresh the water supply on a regular basis. However, herons are no respecters of property. In my area herons moved in and took advantage of unprotected ponds, so plenty of expensive koi carp were eaten. Safety netting protects your fish. You might also need to oxygenate water so that the fish can respire, so a pump might have to be working regularly.
Frogs are a great blessing to a garden, as they eat slugs, but they also need protection from herons. Frogs need somewhere to leap from the water, as they spring out at great speed, so ensure that netting does not impede them. They also like an area with undergrowth to hunt slugs. So ensure that the garden is not totally manicured. Do not put frogs and newts in the same pool, as the frogs will eat the newts.
Ducks will turn clean water filthy very quickly, so think twice about having them in a garden pool. Their eggs will also absorb dirt if left lying in a dirty area, so think carefully about whether to keep them in a garden pool. They are, however, effective and voracious consumers of slugs.