The Importance of Aquatic Plants
Apart from the aesthetical benefits, aquatic plants are a crucial part of a ponds ecosystem. The flora and fauna develop a natural balance whether in ponds, lakes, rivers, streams, canals or reservoirs, ensuring optimum water quality is achieved and reproduction of plants, invertebrates, amphibians and fish can continue.
Aquatic plants play a very important role in absorbing excess waste caused by fish, amphibians and invertebrates. When ammonia is excreted, natural bacteria convert the ammonia to nitrite and another species of bacteria converts it to less toxic nitrate; this is then used by plants and algae to grow.
As with all plants; aquatic plants also produce oxygen into the pond during the daytime, but at night; they produce carbon dioxide, absorbing the oxygen during photosynthesis often having detrimental effect on livestock, especially larger fish such as carp. During the warmer months it is important to have some moving water to help aerate the pond so fish do not suffer. Fish are quite often kept in much higher numbers in ponds compared with the natural environment which will supports less population densities and in greater areas so creating the right balance is crucial.
Without going into filtration, it would be advisable to have a variety of aquatic plants that include oxygenating weeds, marginal’s and lilies for cover. The usual advice for ornamental ponds is to have approximately two thirds of your ponds surface covered in aquatic plants. Introducing some oxygenating weed such as Elodea or marginal’s such as Water Mint or Brooklime are great for absorbing excess nitrate because their roots grow into the pond and absorb directly from the water, they also provide good cover for fish and shade form the sun, helping to prevent string algae.
Marginal aquatic planting creates shade in the shallower areas and give protection to many invertebrates and amphibians such as frogs, newts and tadpoles. Deeper aquatic plants such as lilies and Water Hawthorn also give shade from the Sun, helping to prevent algae.
There are a variety of floating pond plants that are available during the summer months such as Water Lettuce, Hyacinth and Chestnut and also Water Soldier that can often survive winter periods. All these are excellent in giving shade and will all assist in helping to combat algae as well as helping to create a healthy pond for fish, amphibians and invertebrates.
Despite many recommendations about only growing Watercress in running water, it will still grow in ponds. Although not a true aquatic plant; Watercress will trail its roots into the water, but the actual plant normally grows in soil above the water’s edge. Larger plants grow runners directly from the main plant and from these new ones will grow. Watercress will not tolerate stagnant water but a pond that has been cleaned or a new pond will happily allow watercress to grow. The best place to plant it, is near to a waterfall or around the water’s edge. Buy a bunch from the supermarket and put it in a glass of water until the roots have grown, but ensure the water doesn’t stagnate by refreshing it with new. Once the roots have grown, you can plant it outside, ideally in a sunny aspect.