About a month ago, toxic blue-green algae were found at Lake Hefner.
As of Monday, officials say the lake is free of the toxic algae.
The algae may have impacted some wildlife at the lake but officials say oxygen levels at the lake are normal.
"The treatment that we use has no impact on the wildlife in the lake, but I am sure the toxins from the I mean I would make the assumption that the algae is what killed some fish out there," said Leigh Ann Kitsmiller, the laboratory manager at the water quality department.
While the algae were present, the lake was never closed to fishing. Officials said it is okay to eat the fish, you just want to clean them well and avoid eating internal organs.
The lake has now reopened to activities like paddle boarding and wind sailing.
Lake Hefner also serves as one of seven drinking water reservoirs in the area. Kitsmiller said the algae never affected the city's water supply.
"Once it gets into the treatment plant, we also have processes in place that are going to remove all of the toxins and bacteria and stuff from the water," said Kitsmiller.
The city will continue to monitor the water at Lake Hefner twice a week.