The reed bed on the Heath where the fleas are being encouraged to breed

A NEW weapon in the annual battle to keep Hampstead Heath’s Highgate ponds free of toxic algae is no bigger than a fleck of dust.
In recent summers the men’s pond has been closed while boffins try to work out a way to stop algae blooms making the water dangerous for swimmers.
But now they believe they may have the answer – daphnia, a water flea that feasts on the algae.
The blue-green algae forms a paint-like scum on the surface of the water.
It has been responsible for killing wildlife and causes nasty symptoms in swimmers, including vomiting, diarrhoea, itchy eyes, fevers and aches.
Scientists say high levels of naturally occurring phosphorus in some parts of the Heath help create the blooms, which are also triggered by hot weather and calm conditions.
Now a team of Heath workers has built a reed bed in the corner of the model boating pond – upstream from the bathing pond – where the fleas are being encouraged to breed.
They hope the fleas’ appetite for the algae will mean the men’s pond stays open throughout the summer.
Heath ecologists are confident the fleas, normally bought in pet shops to feed to tropical fish and terrapins, will help beat the problem.
Heath superintendent Simon Lee said the tiny algae-busters are just one weapon in the drive to improve water quality at the Heath’s ponds.
He said: “We shall soon be renewing floating nets of barley straw on the ponds which release hydrogen peroxide as they decompose, killing the algae, and installing a second propeller-mixer on the boating pond, which increases the amount of oxygen.
“Improving water quality at the Heath’s ponds is a high priority but a complex task. The emphasis of work at the boating pond reflects the importance of this water to the men’s pond.”
The ponds are fed by a spring in the Vale of Health and Kenwood. Watercourses snake down to the ponds, which eventually run off underground into the now-covered River Fleet.