February 2012. A company is doing the planning and permitting for a 56-acre hobby farm on the island of Oahu, Hawaii. There will be a small pond for ducks which will need aquatic plants to keep it clean. Toxic
chemicals and heavy metals are not factors, just the duck waste. The pond will receive full sun, as well as shade, over the course of a day. Temperatures never reach freezing at the location. We need to try to find species that aren't invasive because environmental review and special permitting is needed for the project. Does anyone have any ideas?
In response, a member said that he had had a similar project installing plants in ponds which receive banana packing shed waste waters (water polishing ponds). The idea was to remove nutrients and solids from the water before it entered the natural watercourse.
There was no information on plant species appropriate to the area for this purpose, however the best advice received from others, was to see if there were suitable species occurring naturally (native). By choosing native species, it meant the plants would not pose an environmental problem. Four species were collected from creeks and drains; from these a native sedge was selected because it had several useful characteristics - easily propagated, emergent but anchored to the pond bottom, and correct vegetation type to trap nutrients and suspended solids. The other three species were rejected because one was found to be an introduced species, and the other two were harder to propagate, and also had less suitable characteristics for catching suspended solids.
The plants have worked out perfectly for this use. A native duckweed, Lemna sp., has covered the open water with the native sedge (Schaenoplectus mucronatus) between. Ducks may offer somewhat different problems as they may feed and uproot/disturb the plants. Fencing off the plants may be needed. Additional aeration may be required - we used small waterfalls between the ponds to provide oxygenation. Paddle aerators are available but they were not needed.
In addition to the aquatic plants, we planted native species found growing close to the waters edge in similar natural habitats. These include trees, shrubs and herbaceous plants. We intentionally only planted one side of the ponds to allow for free air movement across the water surface and made some parts of the ponds deep (greater than 2 m) so there was open water as well.