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AURORA, Colo. (KDVR) – The City of Aurora will be closing the popular Quincy Reservoir for two days to treat the water for a harmful form of algae called Harmful Blue Green.

Opened in 1973, Quincy reservoir used to be a water source for the city of Aurora. Now it’s a source of fun for boating, fishing, hiking and biking.

But as the days grew hotter, something else was growing in the water.

“The Blue Green algae, it was prevalent last year in large bodies of water all throughout the state of Colorado,” said Erin O’Neill of the City of Aurora Parks, Recreation and Open Space.

Blue Green algae is naturally occurring. It grows during summer when warm weather and nutrients, such as phosphorous from fertilizer, can encourage algae overgrowth.

Left untreated, it can be hazardous to plant and wildlife.

“It takes out oxygen from the water and so then it affects plants and species and fish inside the water,” said O’Neill.

The treatment is hydrogen peroxide.

“It is safe for wildlife, it is safe for humans, everything like that so it’s a way of kind of knocking out the algae while also being safe to our patrons,” said O’Neill.

Hydrogen peroxide? Don’t we use that to change the color of our hair?

“I believe it is, yes – Amongst other things, like algae killing,” said O’Neill.