Plants

• Plants are the stars of the water garden show. This is not only because of their aesthetic value, but because they serve multiple functions in maintaining and balancing the water garden. Many plants, but especially underwater plants, oxygenate the water. Good dissolved oxygen levels in the pond keep algae levels low, keep fish or other aquatic animals from suffocating and prevent bad odors coming from the pond. Plants also shade the surface of the water, protecting fish and further reducing the risk of algae buildup. They attract insects that prey on water garden pests, such as mosquitoes. On the banks, bog plants prevent erosion and soften shoreline edges if soil is used.
  
  

Soil

• Many water gardeners try to use decorative stone or otherwise leave the bottom of the water garden soil-less. But soil is a habitat not only for underwater plants, but other underwater creatures that regulate the balance of the pond, such as snails, crayfish, frogs and many more. Soil-borne organisms convert the sludge at the bottom of the pond to useful compounds for plants and keep them from polluting the water. Soil is part of nature's filtering system.
  
  

Fish

• Fish are popular additions to water gardens, but they are also the feature that causes the most problems for amateur water gardeners. Too many fish and the system needs mechanical filtration because fish wastes build up in the water faster than plant materials can soak them up for nutrition. Not only does the waste harm the fish, but it also encourages algae blooms that reduce or eliminate dissolved oxygen in the water and suffocate the fish. A small number of the right type of fish, however, will nibble at weedy plants and consume large quantities of mosquito larvae.
  
  

Equipment

• A balanced pond rarely, if ever, needs additional equipment. However, if a pond is overloaded with fish, it will need a filtration system that includes a pump and filter. Plentiful fish also need high levels of dissolved oxygen, and even a plethora of underwater plants may not be able to keep up. Aerators pump air into the bottom of the water garden to increase the oxygen level in the water. These features require an electricity source readily accessible for the water garden.
  
  

Container

• Contained water gardens don't rely on heavy, impenetrable layers of clay soil or a high water table. They rely on waterproof, synthetic membranes, poured concrete or any variety of pond forms. For small water gardens, whiskey half-barrels make a decorative base, while larger above-ground water gardens may be wooden or concrete structures built specifically for a water garden. Containers that are not impervious to water or that are made of a substance with traces of toxins must first be lined with a pond-grade membrane.