There’s surviving, and then there’s thriving in a literal sewer. A colony of guppies—the same tiny tropical fish people keep in desktop aquariums—has managed to do both for more than 40 years in the waste-choked canals of a Kyiv treatment plant.
Scientists first spotted the fish in the Bortnicheskaya aeration station back in the 1980s. Somehow, instead of croaking in the polluted, smelly water, they multiplied. “Although the water is polluted and smelly, they live there all year round and reproduce successfully, and there are a lot of them,” ichthyologist Yulia Kutsokon told Ukraine’s TSN.
Native to the warm, shallow rivers of Venezuela, Guyana, and Brazil, the guppy (Poecilia reticulata) typically prefers clean, slow-moving water. But this group decided Ukraine’s grimy sewage canal was close enough—thanks to warm discharge water and a strong current that keeps oxygen flowing.
According to Kutsokon, they can only survive in the faster-moving upper part of the canal. Downstream, where sludge collects and the current slows, even they tap out.
Popular Aquarium Fish Built an Underwater Empire in Ukraine’s Wastewater System
They’ve lasted this long because guppies are ridiculously adaptable. They’ve been found in ponds, ditches, and even storm drains around the world. Their hardiness, rapid breeding, and ability to tolerate a range of temperatures and water qualities make them ideal for aquarium owners—and apparently, for life in Soviet-era sewer systems.
Unfortunately, the guppies’ reign is under threat. In recent years, their numbers have declined due to an invasive predator known as the rotan-head (Perccottus glenii), a fish that wandered in and started eating them. Even in the sewers, nothing gold can stay.
Still, the fact that these fish have been swimming, mating, and somehow thriving in Ukraine’s wastewater for decades is a kind of dystopian miracle. It’s also a bizarre reminder of how adaptable life can be, even in places we’d rather not think about.
And while most aquarium fish die when someone dumps them down the toilet, these guppies built a whole damn society down there. They’ve found warmth, oxygen, and just enough space to exist in the least glamorous ecosystem imaginable—and they’ve kept going despite the odds.
It’s weird. It’s gross. But in its way, it’s impressive. The moral of the story? Evolution loves an underdog—even the ones living in sewage.
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