When your pond is built and full of water, you'll naturally want something living in it and this, of course, does not just mean fish. One of the keys to an attractive looking pond is good planting. This is not only aesthetically pleasing but also beneficial to the life in and around the pond.
These are typically fast-growing pondweeds. The term oxygenator is a bit misleading, as the oxygen content added to the water by these plants is fairly minimal. They do, however, help to use up the nitrogenous waste which is a by-product of aquatic livestock, thus helping to maintain the water balance. Another useful function of plants such as these is to provide cover for fish.
As the term suggests, these are plants best suited to the periphery of a pond. Some are at home in the shallow water at the edge, whilst others like to grow next to the pond in order to take advantage of the damp conditions. The latter will often trail into the water. Those in the water itself will again use fish waste as fertiliser and as a result usually produce dense mats of roots, ideal for small aquatic organisms to live in. These creatures, in turn, provide a good food source for the larger inhabitants.
Deep water plants tend to be large and this often makes them unsuitable for all but the largest ponds. However, there are some cultivated varieties to choose from which have been deliberately grown as small or pygmy varieties, ideal for the smaller pond.