The iron oxidising bacterium Leptothrix discophora forms beautiful, fragile and iridescent oil-like films on the surfaces of natural waters rich in iron. Often mistaken for pollution and oil spills, these films are an entirely natural phenomenon. I decided to try my hand at growing this bacteria at home, and simply threw a handful of iron nails into a bucket of collected rain water. Just over a month later, and I have a thriving and iridescent surface community of Leptothrix discophora. I simply provided an appropriate niche, which the bacteria found an exploited. How did they find it? Were they wind blown or were they present in the rain itself?