Warning notices will now be removed from Hemlington Lake following confirmation from the Environment Agency that water is now clear of blue-green algae.
The all-clear follows three tests of the water over three consecutive weeks, revealing the blooms have been removed.
Blue-green algae occur naturally in inland waters, estuaries and the sea, their growth encouraged by warm water temperatures and stable sunny conditions, particularly if the water has a high nutrient content.
Around half of all blooms of the algae produce toxins which can be harmful to humans and some animals if consumed in significant quantities.
These toxins can kill wild animals, farm livestock and domestic pets, while in humans they can cause rashes after skin contact and if swallowed can cause vomiting, diarrhoea, fever and muscle/joint pain.
Staff at Hemlington Lake & Recreation Centre tackled the problem by putting barley straw into the lake, which rots down and gives off a natural chemical to kill off the blooms.
Staff will continue to monitor the lake and deal with any recurrence of the algae accordingly.