TWO thousand dead fish had to be removed from a pond at Castlemorton after being starved of oxygen by mysterious brown algae.

Wardens employed by Malvern Hills Conservators were alerted to the appearance of dead fish at the Mill Pond on Sunday morning.

They received a quick response from the Environment Agency, who tested the water, removed dead fish and set up oxygen equipment.

But the dead fish, chiefly carp, continued floating to the surface for the next two days and by Tuesday around 2,000 had been removed.

"The weather conditions were right for algae to reproduce in the pond, forming an algae bloom," said Dr Alan Starkie, of the Environment Agency.

"Living algae and plants use up oxygen at night and when the algae dies back, oxygen supplies are significantly depleted and fish die from lack of oxygen.

"The situation is aggravated by the urine and faeces of fish and ducks.

The combination of feeding ducks and anglers' bait, together with a shallow pond and warm weather, has encouraged the algae to bloom."

He said oxygen levels dropped, but had now been boosted by the agency's oxygenating equipment and the pond was being checked daily.

Fish numbers are expected to recover naturally but, in the meantime, anglers are being asked to co-operate by not fishing in the Mill Pond for the foreseeable future.

"It is a very popular spot for fishing, but there is not much sport in catching half-dead fish," said the director of the Conservators, Ian Rowat.

"The first day it was the little ones that were dying, but towards the second and third days we were picking up sizeable carp, 12in to 18in in length.

"The tiny fish should put on a spurt of growth now because of the lack of competition."

It was not the first time algae had caused problems at the pond, but the last incident had been 20 years ago, he said.

"It wasn't caused by the blue-green algae everyone knows.

"This one is more of a brown colour and you can't see it on the water, but it multiplies like mad in warm, humid weather," he said.

"When it has used all the oxygen and nutrients it dies back like a desert plant and that could be the end of it for another 20 years."