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DIY Floating Pond Island: Tips For Creating A Floating Wetland

DIY Floating Pond Island: Tips For Creating A Floating Wetland


By: Jackie Carroll

Floating wetlands add beauty and interest to your pond while allowing you to grow a variety of wetland marsh plants. The plant roots grow down into the water, improving the water quality and providing habitat for wildlife. Once planted, these floating islands are much easier to care for than terrestrial gardens, and you’ll never have to water them.

What are Floating Wetlands?

Floating wetlands are container gardens that float on the surface of the water. You can plant a floating pond islands with any wetland marsh plants except trees and shrubs. They make a beautiful addition to any pond.

As the plant roots grow beneath the island, they absorb excess nutrients from fertilizer runoff, animal wastes and other sources. Removing these nutrients from the water reduces the incidence of algae, fish kills and choking weeds. The water beneath a floating wetland is cool and shady, providing habitat for fish and other beneficial organisms.

Plants for Floating Islands

You can use a wide variety of plants for floating islands. Give first consideration to native marsh and wetland plants. Native plants are well-suited to the climate and will thrive in your pond with less maintenance than non-native plants.

Here are some plant suggestions:

  • Pickerelweed – Pickerelweed (Pontederia cordata) has heart-shaped leaves on stems that grow 2 to 4 feet tall. Blue flower spikes bloom at the top of the plant from spring until fall.
  • Marsh hibiscus – Also called rose mallow (Hibiscus moscheutos), march hibiscus grows about a foot tall. The showy hibiscus flowers bloom from midsummer until fall.
  • Narrow-leaved cattails – This variety (Typha angustifolia) has the same characteristic, velvety brown spikes but narrower leaves than that of common cattails. Geese and muskrats feed on the roots.
  • Flag iris – Both yellow (Iris pseudacorus) and blue (I. versicolor) flag iris are lovely irises with thick, dark green leaves and showy flowers in spring.
  • Bulrush – Dark green bulrush (Scirpus atrovirens) is a common sedge with showy seed heads atop 4 to 5-foot stems.
  • Water arum – Water arum (Calla palustris) has heart-shaped leaves and large, white flowers. They give way to red and orange fruit later in the season.

Creating a Floating Wetland

Creating a floating wetland is easy using a floating plastic or foam matrix. You can buy these devices at a pond supply store or order them online. There are two basic types.

One is a floating mat or container that holds organic matter for planting. The other is a series of special containers filled with plants. The containers fit into a floating grid. You can combine several grids to form a large surface area. You’ll find many variations on these two themes.

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Artificial floating islands will help safety of water for Ohioans

Research conducted at the Milliron Research Wetlands at Ohio State Mansfield is testing the effectiveness of artificial floating islands, or AFIs, at removing nutrients from the water. Credit: Courtesy of Zhaozhe Chen

Floating objects covered with plants sit atop a quiet, scenic wetland at Ohio State’s Mansfield campus, but they’re not just for decoration — these structures could promise safer water for Ohioans and the survival of Ohio’s aquatic life in the future.

Zhaozhe Chen, a graduate student in earth sciences who completed the research for his master’s thesis, said he constructed and tested artificial floating islands for their ability to remove excess nutrients from wetlands such as marshes and swamps. Nutrient pollution is one of the most pervasive and costly environmental problems in the U.S., according to the Environmental Protection Agency website.

Ozeas Costa Jr., an associate professor of earth sciences and Chen’s thesis adviser, said nutrient pollution causes the overgrowth of algae. The overgrowths, called algae blooms, release toxins that can cause health issues, lower water quality, harm food resources and significantly pollute water. The blooms also cause a decrease in oxygen in the water that leads to the illness and death of many fish and aquatic life.

Initially planned to be conducted at Ohio State’s main campus in Mirror Lake, the research was approved to take place at the Milliron Research Wetlands after COVID-19 limited Columbus campus research activity, Costa said.

The experiment consists of three cells that each contain six individual floating islands and are placed in the wetland, Chen said. The floating islands are made with PVC pipes to provide buoyancy and have plant shoots growing above the water and plant roots underwater.

Along with the natural experiment, Chen said they are running an additional control experiment with more artificial floating islands in controlled settings to test exactly how much and what types of nutrients the islands remove from the water.

“For Lake Erie or Maumee Bay, where the nutrient pollution is very, very extensive in those regions, apparently, the plants themselves are not enough,” Chen said. “So, [artificial floating islands] can provide extra help to that process.”

Chen said the islands remove nutrients from the water using the plants atop them: The plants absorb nutrients for their own growth while the underwater root systems trap suspended solids to remove nutrients. Bacteria can also form on the plants and floating structures that remove nutrients through chemical processes.

Costa said the use of artificial floating islands and plants as a natural way to eliminate waste water began about 40 years ago in North America and is currently a popular practice in Asia.

“Plants, naturally, they filter out metals, nutrients, pathogens and other types of contaminants that are in water,” Costa said. “That’s why wetlands are so good at cleaning up wastewater.”

Chen said if the research proves successful at removing excess nutrients, it could be upscaled and serve as a cheap solution to clean nutrient-polluted water bodies such as lakes and rivers.

“We do not have to invest billions of dollars to build new wastewater treatment facilities. It is a natural way of solving the problem because it uses the things that plants already do,” Costa said. “They are low cost, environmentally friendly and highly effective ways of dealing with nutrient pollution.”

Through replicating experiments in Asia, Chen said he adapted the research to fit the conditions and species found in Ohio’s wetlands by using aquatic plant species native to Ohio and accounting for the region’s climate.

Costa said testing began in April and the artificial floating islands were installed in May. From there, they collected samples until they removed the islands near the end of October.

The research had to be conducted from April to September, Costa said, because when temperatures are too low, the plants start decaying.

“When that happens, not only do they stop doing what we want them to do, but they also start putting nutrients back in the water,” Costa said.

Chen said he is currently analyzing data from the experiment’s weekly samples to discern the effectiveness of the floating islands at nutrient removal and the contribution of each type of removal process at extracting nutrients from the water. Until that data is analyzed, results are tentative, but initial observations look promising.

Chen said the research will continue following his master’s thesis in the spring. The research was funded by grants from the Ohio State Sustainability Institute and the School of Earth Sciences’ Friends of Orton Hall.


The McLaren Difference: Applied Ingenuity

Small-scale floating wetlands have failed due to maintenance and short service lives — the more thriving the wetland became the heavier and more unbalanced the structure, causing them to tip or sink. McLaren and their project team took into consideration the lessons learned from these previous structures and designed a floating wetland with inert plastic materials, and an adjustable buoyancy system to counteract the accumulation of marine growth. This design solution blurs the boundaries between natural and structured urban environments, showing they can coexist and flourish together.

The 1-year prototyping phase started in the spring of 2017. A 15 foot by 20-foot prototype that anchors on two sets of existing guide pipe piles was developed to 60% design. The project team determined the best-detailing practices and operational limitations of the floating wetland before finalizing 100% construction drawings, saving the NAIB money, and while designing the most effective project.

The McLaren team found that the most prudent and cost-effective solution for creating stability in the low freeboard required by the plantings (highest marsh levels only extend 6 inches above water) was adding a controllable ballast system, counteracting the effects of added marine growth weight. By calculating the sinking rates from the prototype, the design team arrived at an estimated fouling load of 1.5 pounds per square foot per year, which will gradually taper off to near zero before year 10.

The controllable ballast system utilizes high-density polyethylene (HDPE) 30-inch diameter pontoons with adjustable water fill, referred to as the “dynamic buoyancy” system. The floating wetland is designed to easily accommodate additional pontoons being floated under the wetland, attached, and then pumped full of air to provide supplemental buoyancy. A portion of the HDPE pontoons will be filled with closed-cell marine foam, and will provide an unchanging buoyant force, referred to as the “static buoyancy system.” Both the foam fill and static buoyant force can be calibrated to match the weight of the wetland’s structural components, PET, and plantings.

With very little buoyancy in reserve to counteract the added weight of maintenance workers and waves, a reserve flotation system was engineered for added buoyancy and stability, allowing employees to stand on the edge of the wetland without it swamping. Cavities within the PET will be filled for the reserve system, with spray-applied closed cell marine foam, and carefully spaced in linear strips to not interfere with plantings. As the PET colonizes with biological material overtime and void space reduces, the wetland is predicted to become more stable and improve its ability to support persons and wave loads.

The top structural layer consists of 2-inch-thick fiberglass grating. The grating is environmentally inert, lightweight, and provides easy means of fastening the PET and fiber-reinforced polymer (FRP) threaded rods above the structure. The fiberglass grating also provides a sufficiently rigid base to support laminated PET layers with foot traffic and not cause damage. The wetland is designed to accommodate FEMA 100-year flood levels, resist winds, waves, and currents from a 100-year storm, locally support 40 pounds per square foot of personnel loading, have a service life of 30 years with minimal maintenance, and be able to withstand the catastrophic loss of a pontoon’s buoyancy without structural failure.


Lines of defense

An illustration provided by the N.C. Land and Water Fund shows environmental and aesthetic benefits of a floating wetland island. (Illustration courtesy Iowa State University)

The northern arm of Greenfield Lake receives stormwater drainage from a stream that passes underneath Lake Shore Drive. It collects water from a 173-acre watershed that is largely developed, consisting of numerous home roofs, driveways, and paved roads — all impervious surfaces that contribute to polluted stormwater runoff.

Dr. Hunt said that if the proposal goes through, his team will place lines of connected floating islands stretching across the northern arm: one near the stream’s entrance into the lake, and another approximately 100 feet downstream. He described it within the context of old Revolutionary War tactics.

“Think of floating islands connected as a line of troops that the water has to pass through. If the water goes through the first line of defense, then in a hundred feet it must pass through a second line of defense,” Hunt said.

His team will measure water quality samples taken immediately after the first line to see if there is any improvement, as well as after the second line to see if there is continued improvement as the water moves to the broader areas of the lake. Although the project is not intended to fix the pollution problems at the lake, he said, “we think it is a part of a larger strategy to address them.”

“And if they can work, we might see them more in Greenfield Lake and we might see them more in other ponds in Wilmington,” he said.

Th excessive amount of nitrogen entering the lake is specifically concerning, he said, as nitrogen is found in rainfall that hits rooftops or roadways and there is nothing to filter it out before it enters the lake.

Although he is an engineer unqualified to measure people’s response to the visual aesthetics of the floating island — especially those walking the Greenfield Lake Park Trail that loops around the lake — he said “anecdotally, that will certainly be something we look at.”

Hunt is also helping Cape Fear River Watch on another water quality improvement project on Greenfield Lake, which further motivates him to choose the lake for his own project. On top of that, the city of Wilmington has “been a very good cooperator” with N.C. State in the past, and they are pushing for this project as well. (The city agreed to a small financial match, according to the LWF. If the project had been approved for the initially requested $187,000, the city would have contributed $3,457, with N.C. State’s contribution estimated at $19,090.)

He said the city has agreed to perform maintenance of the floating islands.

Choosing Greenfield Lake would be beneficial not only because the city, along with partners like UNCW and Cape Fear River Watch, have expressed growing interest in improving the lake’s water quality, but because it would encourage use of the floating islands across a region where stormwater runoff has become an increasing concern as development continues to sprawl, according to Hunt.

But plenty still needs to be ironed out in the coming weeks. According to Summer, an LWF program manager will negotiate with Hunt on the project’s scope — what he can do with $100,000 instead of $187,000 — over the next several weeks before anything is finalized.

“It will take a lot more work, trust me, but you gotta start somewhere,” Hunt said. “I feel like this project, plus the one the Cape Fear River Watch is shepherding, are really important starts to an eventual improvement in Greenfield Lake.”

Noah Blanton, who studied marine biology at UNCW, walks along a bridge stretching across Greenfield Lake’s north arm Thursday evening. He said he supports the idea of floating wetland islands if they are scientifically proven to improve the lake’s water quality and will not upset the ecological balance of the lake’s ecosystem. (Port City Daily photo/Mark Darrough)

Send tips and comments to the reporter at [email protected] or (970) 413-3815

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  • Environmentalists are innovating low cost but effective natural techniques can be used to clean city lakes that are choking with pollutants.
  • Floating Treatment Wetlands are ingenious bamboo raft with its sides made of thermocol blocks and plastic bottles which are chemically inert.
  • Wetland plants, mosquito repellents and ornamental plants like cattails, bulrush, citronella, canna, hibiscus, fountain grass, flowering herbs, tulsi and ashwagandha are planted on the raft

The city of gardens and lakes - Bengaluru - could largely benefit it adopts the Floating Wetlands programme with hydroponic plants that clean polluted waters. A radical new method is fast emerging as an effective and sustainable solution to increasing pollution in urban lakes.

Called floating treatment wetlands (FTW), they are artificial islands with plants that stay afloat on the lake, reports the India Water Portal.

The report says that this is already being successfully implemented in Hauz Khas lake in Delhi. Another lake to benefit from this treatment method is Neknampur Lake on the outskirts of Hyderabad city.

What are FTWs or floating treatment wetlands?

  1. A bamboo raft with its sides made of thermo-col blocks and plastic bottles which are chemically inert.
  2. A layer of gunny sacking stretches across the raft’s bottom to create a tray that holds a two-centimetre layer of gravel.
  3. Saplings have been planted in the soil with their roots reaching into the water.

Around 3500 saplings of different varieties can be placed on 3000 sq. ft. raft.
The types of plants are wetland plants, mosquito repellents and ornamental plants like cattails, bulrush, citronella, canna, hibiscus, fountain grass, flowering herbs, tulsi and ashwagandha.
The plants absorb the high levels of phosphorus and nitrogen in the sewage water entering the lake.

A Bengaluru-based company has also developed a floating wetland on which hydroponic plants can be grown. this in turn can improve the quality of the water wherever the wetland is deployed.

Also called Floating Wetlands:
Floating wetlands are small artificial platforms which allow hydroponic plants to grow with their roots spreading through the platform into the water.

AlphaMERS, the company that has developed this eco-friendly idea, believes these wetlands can be deployed in lake inlets or even stormwater drains.

"This is basically as floating wetland developed by us for growing hydroponic plants in water bodies which are polluted. The roots of the hydroponic plants feed on the nutrients in the flowing waters and clean them. Even sewage water is considered a nutrient for these plant roots which absorb and thrive on the pollutants," Captain DC Shekhar, the Executive Director of AlphaMERS told the Bangalore Mirror.

What are these floating islands made of?

  1. Sturdy aluminium that can withstand corrosion
  2. PVC pipes
  3. Hydroponic plants

Quoting Wetlands restore lakes’ quality and health

In Bangalore, we often find a spontaneous or natural growth of vegetation in our tanks when the sewage is piped into them, and we find that when water filters through this vegetation, it tends to improve the water quality. This has pushed us to think about engineering wetlands, to clean our lakes and tanks. Let us look at engineered wetlands and then move to spontaneous wetlands.


Floating Treatment Wetlands:

Keeping our fresh water clean and healthy

Why Do We Need Floating TREATMENT Wetlands?

Freshwater lakes around the world, especially shallow lakes, are in trouble.

Urbanization, waste treatment, landscape changes, agriculture, and natural resource extraction cause runoff of nutrients, contaminants, petroleum products, and organic materials to freshwater lakes around the world.

Biological treatment is possible, however, by harnessing the natural ability of plants and microbes to absorb nutrients (such as phosphorus and nitrogen) and break down contaminants through biological processes known as bioremediation.

Wetlands have the natural capacity to to absorb nutrients and break down contaminants.

Wetlands have the natural capacity to to absorb nutrients and break down contaminants.

The Magic of Wetlands

The use of wetlands for bioremediation to capture and remove contaminants and nutrients is widely practiced around the world.

Wetlands can improve improve water quality of storm water runoff and manage watershed nutrients, as well as treatment of wastewater and other industrial contaminants.

Wetlands rely on natural processes to biologically filter water as it passes through shallow areas of dense aquatic vegetation and permeable bottom soils. The primary mechanisms for nutrient removal is transformation and uptake by microbes and plants, assimilation and absorption into organic and inorganic sediments, and converted into gas through volatilization. Aquatic plants, both above the water and submersed, take up and remove these elements from the sediment and water column into their plant material or biomass.


What Are Floating Wetlands: Growing Plants For Floating Islands - garden

About the floating island standard square models

While we can custom create any shape or size, we offer 3 standard square models for clients looking to start small and add on as time allows. Our modular islands make it easy for transport and for those who want to build a floating island. These modular wetlands / floating islands are readily available in the following 3 sizes.

3 x 3 foot (approximately 9 square ft)

4 x 4 foot (approximately 16 square ft)

5 x 5 foot (approximately 25 square ft)

*Don’t see what you are looking for? At Floating Islands West, we are able to customize just about any shape or size for the perfect floating island or modular wetland. Just let us know.

Each of our floating island models are manufactured with individual planting pockets and can be planted with your choice of aquatic or terrestrial plants. If you are searching for a nesting island for ducks, or even a swan habitat island, these floating islands will allow you the flexibility that you need. The square or modular island design allows you to buy now and add on later, creating a bigger island as time and budget allow.

From the moment your BioHaven® is placed into the water, even prior to adding plants, our bio matrix (proprietary design) kick starts the water treatment process through microbial activity. This is not your regular swan nesting island, or a simple basking platform for a pond turtle, we offer a genuine floating treatment island backed by years of research. We recognize the need for clean & clear pond water by using the islands in our own pond, we enjoy zero pond odor while keeping the pond water clear, the natural way. A healthy pond = a happy ecosystem & BioHaven floating islands are the perfect pond product to control algae, while providing shade and cover for your fish.

Remember, we can customize any island to meet the needs of your pond or lake. Let us know what you want.


Watch the video: How to Plant Pond Plants Without Soil: Solving Plant Needs