If you are using a soft liner your water garden or fish pond can take any shape you like, square, round, oblong or just about anything else that your imagination can think of. If you are using a rigid or preformed pond then you are probably looking at a kidney shaped liner, this is the most popular. It is not the shape of the garden pond that gives it it's charm or character, it is the water plants, fish and the plants that surround the pond.

Basically think of pond styles to be one of two formal and informal designs.

Formal pond styles have clean straight lines and geometric shapes. They have rigid borders made of brick, preformed tiles or rocks. Formal garden ponds are used as reflecting pools. Meaning they are very calm and reflect the surrounding trees and flowers. You don't normally see this style of water garden in backyards.

Rectangles and squares are thought of to be formal styles and the more they are stretched to being oval the more informal it looks. Which means kidney and pie shapes are informal styles.

Informal garden ponds have curving fluid lines that flow without defined edges into the surrounding gardens and vegetation. They have a more natural appearance and function. Unlike formal styles the plants are not used as a decoration or ornament but as the main feature. Waterfalls are normally added to this type of design. Edging compliments the landscaping which can be irregular and hilly. Use large rocks and river rocks on the bottom and edges of the pond, which makes it seem more natural.

Rectangles are the easiest to install, they are easier to dig a hole for and when using soft liners you only have to make a few folds in the corners. Preformed ponds like kidney shapes are even easier to install. Free formed, where you define the shape by digging and then lining with a soft pond liner are more difficult and the most expensive water gardens to install yourself. They require that you buy almost twice as much liner than you think you will need. If you are installing it yourself avoid shapes that produce arms or very irregular designs, it will be a nightmare trying to get the liners to fit.

Just remember what ever shape you choose, it will not be very apparent once the surrounding plants mature. So you see it is not that important, just go with the easiest to install and decorate with beautiful plants and fish. You can read more information about and pond kits and water gardening here.