Water gardens, also known as aquatic gardens, are a type of man-made water feature. A water garden is defined as any interior or exterior landscape or architectural element whose primarily purpose is to house, display, or propagate a particular species or variety of aquatic plant. Although a water garden's primary focus is on plants, they will sometimes also house ornamental fish, in which case the feature will be a fish pond.
Although water gardens can be almost any size or depth, they are typically small and relatively shallow, generally less than twenty inches in depth. This is because most aquatic plants are depth sensitive and require a specific water depth in order to thrive. The particular species inhabiting each water garden will ultimately determine the actual surface area and depth required.
When the aquatic flora and fauna is balanced, an aquatic ecosystem is created that supports sustainable water quality/water clarity. Elements such as: fountains, statuary, waterfalls, boulders, underwater lighting, lining treatments, edging detailing, in-water and bankside planting and watercourses can be combined with the pool to add visual interest and integration with the local landscape and environment.
Water gardens, and all water features in general have been a part of public and private gardens since ancient Persian gardens and Chinese gardens. Water features have been present and well represented in every era and culture that has included gardens in their landscape and architectural environments. Up until the rise of the industrial age, that introduced the modern water pump, water was not recirculated, but was diverted from rivers and springs into the water garden, exiting into agricultural fields or natural watercourses. Water features were historically used for plant and fish production for food purposes as well as ornamental aesthetics.
Though a water garden is restricted to a particular type of natural or man-made water feature, used for a relatively specific purpose or intended use, there are many other types of water feature types, styles and designs.
Types of water features 
- Natural Water Feature
- Man-made Water Feature
- Naturalistic Water Feature
- Disappearing Water Feature
- Live Water Feature
- Sterile Water Feature
- Bog Garden
- Rain Garden/Bio Retention System/Rain Harvesting
- Aquatic Container Garden
- Pool/Shallow Pool/Tide Pool
- Reflection Pool/Reflecting Pool
- Formal Pool
- Swimming Pool
- Pond/Fish Pond/Backyard Pond/Garden Pond
- Naturalistic pond
- Wildlife Pond/Habitat Pond
- Koi Pond
- Swimming Pond
- Water Courses
- Weeping Wall
- Water Wall
- Fountain/Formal Fountain
- Disappearing Fountain
- Tabletop Fountain
- Wall Fountain
- Spitter Fountain
- Bubbler Fountain
- Floating Fountain
- Water Falls
- Lotus pool
- Rice paddy
- Riparian zone restoration
- Wildlife garden - with water-source component.
- Stream pool
- Plunge pool
- Plunge basin
- Spring (hydrology)
- Seep (hydrology)
- Mangrove swamp habitat
- Wild River
- Halka lever
Water follies 
In the sixteenth century, Europe had a renewed interest in Greek thought and philosophy lincluding the works of Hero of Alexandria about hydraulics and pneumatics. His devices, such as temple doors operated by invisible weights or flowing liquids, and mechanical singing birds powered by steam, motivated several European palaces to create similar clever devices to enhance their public image.
In Italy several royal houses constructed large water gardens incorporating mechanical devices in water settings. The best-known is the Villa d'Este at Tivoli, constructed in 1550 AD. A hill cascaded with many fountains and grottoes, some with water-driven figures that moved or spouted water. Popularity spread across Europe with the well known water garden at Hellbrunn Palace built, with many water-powered human and animal performing figures and puppet theaters, and folly fountains that erupted without notice to surprise one.
Stream gardens 
On a constructed stream, placing rocks in the path of the water makes small patterns, rapids and waterfalls. The rocks disrupt the waterflow, causing splashing and bubbles to form, which can make pleasant sounds and micro-habitats for plants, fish, and wildlife. Well placed rocks can stimulate splashing water that adds oxygen to prevent hypoxia, with the more bubbles - the more dissolved oxygen in the water.
Aquatic flora 
Water garden plants are divided into three main categories: submerged, marginal, and floating.
- Submerged plants are those that live almost completely under the water, sometimes with leaves or flowers that grow to the surface such as with the water lily. These plants are placed in a pond or container usually 1–2 ft (0.30–0.61 m) below the water surface. Some of these plants are called oxygenators because they create oxygen for the fish that live in a pond. Examples of submerged plants are:
- Marginal plants are those that live with their roots under the water but the rest of the plant above the surface. These are usually placed so that the top of the pot is at or barely below the water level. Examples of these are:
- Floating plants are those that are not anchored to the soil at all, but are free-floating on the surface. In water gardening, these are often used as a provider of shade to reduce algae growth in a pond. These are often extremely fast growing/multiplying. Examples of these are:
Algae are found in almost all ponds. There are hundreds of species of algae that can grow in garden ponds but they are only usually noticed when they become abundant. Algae often grow in very high densities in ponds because of the high nutrient levels that are typical of garden ponds. Generally algae attaches itself to the sides of the pond and remains innocuous. Some species of algae, such as "blanket weed", can grow up to a foot a day under ideal conditions and can rapidly clog a garden pond. On the other hand, free floating algae are microscopic and are what cause pond water to appear green. Blanket weed is actually a sign that the water is clean and well balanced, although it is unsightly. Green water (free floating algae) means there are too many nutrients in the water, usually from rotting vegetation or too many fish for the space. Killing the free floating algae with chemicals will often cause it to die, rot, and then make the problem even worse as more nutrients enter the water. Adding more floating or submerged (unpotted) plants can help with the green water, as they can take the nutrients out of the water. There are also filters that can be installed to remove the nutrients and all types of algae from the water. Many ponds naturally go green first thing in the spring, and then clear up.
Often the reason for having a pond in a garden is to keep fish, often koi, though many people keep goldfish. Both are hardy, colorful fish which require no special heating, provided the pond is located in an area which does not have extremes of temperature that would affect the fish. If fish are kept, pumps and filtration devices are usually needed in order to keep enough oxygen in the water to support them. In winter, a small heater may need to be used in cold climates to keep the water from freezing solid. Examples of common pond fish include:
- Goldfish (Common, Comet, Shubunkin varieties, Wakin and the Fantail varieties. With the possible exception of some of the fantail varieties, the fancy goldfish are not suited to pond life.)
- Crucian carp
Garden ponds can attract attention from predators such as (in North America) raccoons, Herons, snakes, and domestic cats. These predators can be a danger to fish. Owners of koi are often particularly careful to create protected areas as some varieties are very expensive.
See also 
- Landscape architecture
- Rain garden
- Biochemical oxygen demand
- Chemical oxygen demand
- Wastewater quality indicators
- Garden pond
- Koi pond
Index categories 
- James Burke, Connections (Little, Brown and Co., 1978/1995), p. 106
- Dugout Pond Aeration Flash Animation
- North American Water Garden Society
- WikiHow: Build A Water Garden in 20 Steps
- Pond Conservation: Advice on garden ponds for wildlife