Oxygenating plants are growing fast and will keep a pond clear and algae free. They grow underwater and assimilate nutrients from the water through their leaves and they release oxygen. This why they form an important basis for the natural equilibrium in a pond, whereas they are extremely useful for keeping the water clear and healthy.
The extent of growth is determined by the presence of light, temperature (12-25°C), nutrients, water quality and CO2. If they grow badly or if they do not grow at all this can usually be caused by the water quality and a too low supply of CO2. The chance of algal growth will quickly increase then.
What oxygenating plants do you choose?
Not all oxygenating plants will produce oxygen during the whole season. For this reason it is important to alternate and vary this species of plants. This will make the chance of algal growth het slightest. For spring and winter water-crowfoot (Ranunculus aquatilis) is to be recommended and in summer and autumn hornwort (Ceratophyllum demersum), pondweed or waterweed are to be preferred. Other well-known oxygenating plants are mare’s-tail (Hippuris vulgaris) and water violet (Hottonia palustris).
In existing ponds with many algae – green water and/or fibrous algae – it is not wise to put oxygenating plants. Algae will assimilate all the CO2 present from the water and as a result new plants can not properly grow.
Putting oxygenating plants
Put the plants under water, in coarse sand, gravel, clay pellets or special growth substrate. In nature these plants will root directly in the bottom. In most ponds this is inconvenient, because liner is lying on the bottom or a preformed pond has been used. You are therefore advised to use always pond baskets and to remove first seals and strips. Put your oxygenating plants in a pond which has a proper water quality (rich in minerals, so hard water) and enough CO2, then they will keep the water clear and algae-free. Opinions are varying about the number of oxygenating plants required to obtain clear water, however, a rule of thumb is 5 bunches per 1,000 litres of water.
When do you plant your oxygenating plants?
Newly installed ponds contain in the beginning only few micro-organisms and consequently they have a poor supply of CO2. Before putting in the plants, it is wise to let a pond develop for about 4 weeks’. Plant them preferably in their growth period, between April and June. After planting they will keep the water clear and algae free. If you want to put in oxygenating plants at the same time, oxygen will have to added to the water. For this purpose you can use so-called CO2 Tabs.
Maintenance of oxygenating plants
For local fertilization of oxygenating plants special fertilization balls have been developed.
Oxygenating plants give a clear outlook on ponds! You can buy them in garden centres and pet and pond specialist shops.