Essex Rivers Hub

Darren Tansley, Essex Wildlife Trust's Water for Wildlife Officer, worked with landowners in Sible Hedingham to improve a lake that was previously a carp fishing lake.

The lake is no longer fished and the carp have been removed and is now left to become a wildlife area. The quality of the water within the lake is poor

due to increased nutrients from the fish and lacks habitats within the lake itself. Darren saw this as an opportunity to try out floating islands called BioHavens. These islands not only create habitats within the lake but it is hoped that they will improve water quality through their clever design. Below is a description of how they work:

'BioHaven Floating Wetland Technology is designed around the same principles as a wetland: utilising the natural processes of plants and microbes to improve water quality. BioHavens are man-made floating islands, the proprietary design enables plants and microbes to live in ultra-high concentrations, exponentially higher than those found in naturally occurring or constructed wetlands.

Beneath the BioHaven, a hanging network of roots, rhizomes and attached biofilm is formed. This provides a huge active surface area for biochemical processes, as well as physical processes such as filtering and entrapment. The general design objective is to maximise the contact between the root/biofilm network and the polluted water.

BioHaven® has been specifically designed to mimic a natural wetland; these habitats are extremely valuable environments and provide a broad range of ecosystem services.

BioHaven doesn't rely on any form of external buoyancy; its deep matrix allows emergent vegetation to naturalise, establishing extensive roots that grow into the water and provides a year round enhancement.

BioHaven can accommodate gravel finishes, otter holts, artificial sand martin banks or beautiful combinations of emergent and terrestrial vegetation, tailored to specifically target habitat creation for key species.'

The BioHavens are uniquely designed for each location, with a combination of plants that suit the needs of the area they are being installed into. The company that created and installed the BioHavens is Frog Environmental and if you would like to know more please follow this link.

The photos show some of the Conservation team from Essex Wildlife Trust and the Frog Environmental Team, including Richard Haines a founding partner of the company, assembling and installing the islands in the lake in Sible Hedingham.

It will be interesting to see how the lake will improve with the introduction of the BioHavens and the lake will continue to be monitored to see what impact they have. We will keep you informed of what the results are and any similar projects that we are involved in.


River Colne

WFD water body status


WFD overall status objective

Good Ecological Status by 2027

Project type

Improving Water Quality

Project lead

Essex Wildlife Trust

Contact for more information

This email address is being protected from spambots. You need JavaScript enabled to view it.

Website key stakeholders:

Environment Agency logo      Essex Wildlife Trust logo           

Design by LTD Design Consultants and build by Garganey Consulting based on an original concept by Herts and Middlesex Wildlife Trust