Yeah, I am not convinced they are the best chelators either, however, they are chelators, and there is nothing that is cheaper or better.
http://healthland.time.com/2013/09/12/cilantro-more-than-an-herb-it-can-purify-water-too/
After testing various samples of plants from cacti to flowers, the researchers determined that cilantro is the most prevalent and powerful so-called bioabsorbant material in the area. Bioabsorption is the scientific term for using organic materials often found in plants, that when dried, could replace the charcoal currently used in filters.
They are bitter tasting herbs. From an evolutionary perspective, why is bitter there? Bitter is a poison.
However, if we consider how toxic soap is, or how bitter tasting it is, one has to wonder why these bottom feeders are attracted to bitter flavors, and why they live the longest in thier eco-systems, respectively.
It's the catfish that are attracted to the soap. No other fish. They live the longest, and they basically feed off the bottom of the lake, in the dirt.