Other natural things that can be use as a filter?

Question

I was seting up a water filter as an experiment and was tasked to used natural materials to make a water filter, for example, use crush seeds of moringa olefera....

Was thinking what other things with the correct properties can be used to make part of the water filter. Some common ones are like coconut husk, and charcoal. Any others examples?

Answer 1

sand filter

http://en.wikipedia.org/wiki/Slow_sand_f...

moss

Answer 2

Water peculating through a minimum of 3 feet of soil, this removes most toxins or slowed down in a wet land before it moves on to streams, and bodies of water, mainly to reduce nitrogen.