Outside of Chicago, there is a US Department of Energy physics lab called Fermilab that specializes in high-energy particle physics. The lab mostly looks like green fields, but underground there is a high-energy particle accelerator, which until 2011 was the second-largest in the world (in 2011 it was shut down due to funding shortages), behind the famous LHC at CERN.
One of the coolest things about the enormous lab, though, is the miles of pond that it features. The photo above is of the Ring Pond at Fermilab, and the hundreds and hundreds of Nelumbo lutea, or American Lotus, that reside in it. Now, you might look at those incredibly abundant lotuses sitting above a particle physics lab and think “radiation!”, but this isn’t the case. These ponds are actually perfectly safe, and the general public can go see the grounds (open from dawn to dusk). You can even fish in these ponds with an Illinois fishing license and bring your dog to walk the area.
Experienced pond owners can probably figure out on their own the main reason that these lotuses are so abundant: they’ve been there since the seventies, and had a lot of time to spread and grow great tubers. They were planted in these ponds when the lab was under the direction of the lab’s first director, Robert Wilson, who insisted that the lab be a beautiful part of the local landscape (the lab also has a herd of bison that live on the grounds). It probably also helps that the pond is kept at a steady depth from rainwater reservoirs. The water in the Ring Pond is used to cool the enormous electromagnets that power the particle accelerator, so the water is most likely somewhat warmer than it otherwise might be. The lab uses large fountains to keep the water cool when necessary, and to aerate the water to keep the algae under control (too much algae build-up can cause problems with the magnet cooling plumbing). Essentially it’s carefully kept like a larger scale version of many of your ponds, except that these ponds have played a key role in some of the most important physics discoveries of the last half century.
(Image credits to US Department of Energy and FNAL.gov)