Algae levels at Okawa Bay on Lake Rotoiti are reduced following treatment with a modified zeolite product called Aqual P.

Bay of Plenty Regional Council lakes operations manager Andy Bruere says the treatment was designed to prevent a bloom from occurring, which had potential effects on people's use and enjoyment of the lake.

The presence of blue-green algae in high concentrations can close the lake to swimmers and boaties.

'The regional council has experience with the application of Aqual P on Lake Okaro and tests have shown it is safe to use in the natural environment.

'It was applied to that lake in 2007 and 2009 to deal with eutrophication problems (where nutrients enter the lake and deplete oxygen).

'The product will rapidly settle and flocculate algae, and lock up phosphorus in the water column.”

Andy says the treatment was trialled at Okawa Bay because the algae was potentially toxic and the location was a good spot to undertake the technique.

A slurry was applied to Okawa Bay from a helicopter to lock up phosphorous and drop the algae to the bottom of the lake.

Okawa Bay residents were given information about the process.