Te Arawa Lakes Trust says a floating wetland the size of a rugby field, which is designed to remove tonnes of phosphorus and nitrogen each year from Lake Rotorua, is working well.
The trust helped fund the $900,000 structure, made from recycled plastic bottles and 20,000 native flaxes, which was launched in August last year.
Trust chairman Toby Curtis says if more wetlands could be built, the lake would be cleaned up almost overnight.
He says last year on a visit to China he saw the concept of a wetland to improve water quality being used very successfully.
Mr Curtis says the idea of using a wetland to clean up Lake Rotorua fits in well with the iwi's kaitiakitanga (conservation responsibility).
He says the trust is waiting for the National Institute of Water and Atmospheric Research to complete a study of what benefit the wetland is having for the population of kura (fresh water crayfish) in the lake.