Cardiff woodland stream turned fluorescent blue
![Cardiff woodland stream turned fluorescent blue](https://i2-prod.walesonline.co.uk/incoming/article25951583.ece/ALTERNATES/s615/0_Untitled-design-14.png)
Perplexed walkers have taken to social media, but there's actually a perfectly reasonable explanation behind it
Perplexed walkers have taken to social media, but there's actually a perfectly reasonable explanation behind it