Sunlight
A balance of sun and shade is required. Healthy plant growth requires sunshine, yet too much sun will cause algae problems.
Trees
A location away from overhanging trees is best to prevent needles and leaves from clogging and polluting the water. Small specimen trees can add colour and life to your pond without the problems of larger varieties.
Viewing
Allow your pond to be the centre attraction in your yard. Check the angles from which you will view your pond. Start with the angles from your deck, patio, or from the windows of your home.
PHYSICAL CONSIDERATIONS
To determine the optimum pond size there are a few key factors to keep in mind. First, it is important to consider the size of the area into which the pond must fit. If the pond is too small you will not achieve your desired effect. On the other hand, if the pond is too large for the area, there will not be enough room for stonework or marginal plantings that are often necessary to create a natural looking setting for the pond.
The second important factor is the type of plant and aquatic life you would like your pond to sustain. For example, keeping your fish over the winter months can be greatly simplified by increasing the depth of your pond.
A deep pond will also be more balanced and easier to maintain because the water will remain at a more constant temperature.
Water lilies and other aquatic plants prefer fairly still surface conditions. So, if you are planning to have a fountain or waterfall just make sure the pond is large enough to keep plants several feet away where the water will be calmer.