AN infestation of algae has led to “utter carnage” in a lake, causing more than 1,000 fish to die.
Hundreds more large carp, bream, tench and eels have been left gasping for air in Southmere Lake, Thamesmead, while officers from the Environment Agency have tried to deal with the problem.
Warm weather has caused blue-green algae to bloom in the water, causing the lake’s oxygen levels to plummet.
People living nearby called the agency yesterday after noticing huge numbers of dead fish.
Anne Grant, who walks her two dogs Santa and Jimmy by the lake, said: “There were so many huge fish just dead and you could see all the little ones lying on the bottom.
“There were dead fish everywhere - it was utter carnage. I thought we were going to lose the whole lot.”
The 58-year-old, from Plumstead, said: “One of my dogs jumped in the lake and he came out bright green. I was worried about him because the algae is toxic.”
Members of the Southmere Angling Syndicate have been at the scene, trying to save some of the lake’s wildlife, which includes enormous carp up to three feet long and eels which may have dwelt there since the lake was first made.
The fishermen, who have pulled out around 17 large carp from the water, say they alerted Gallions housing association, which manages the lake, to the algae problem around six weeks ago.
Three aerators have now been put in the water to replenish its oxygen. 
Environment Agency technical specialist Tom Cousins said: “This is a serious incident which has affected a large number of fish. Many hundreds have already died and it seems the incident has not yet run its course.”
“From past experience we know that reoxygenating the water is the most effective way to help the fish after an algal bloom and the fish are responding to this well so far. We could really do with some rain, wind and cooler weather to help naturally aerate the water.”
He said the agency would try to introduce more marginal plants to the lake in an effort to try and stop something similar happening again. 
A spokesman for Gallions said : “Due to the current weather conditions enhancing the formation of algae we have been monitoring the lake and samples were taken by an independent expert on July 12, 16, 23 and 29.
“We were advised that we needed to close the lake as a precaution and to place barley straw in the lake which we have done.
“Continuous monitoring of the lake is in place and we are doing all we can to try and limit this naturally occurring problem. “
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