Yeah, great link, mathis, thanks
Dean, I did something similar than outlined in the link.
I tore lettuce, some fresh and some that was going a little bad in a plastic container with tank water. Put the lid on and let it set on a sunny window sill.
About 3 days later....Wa La...green water. I filtered the water through a coffee filter into a separate container to get the lettuce and other nasty stuff out. I left the lid off the 2nd container because I read the Infusoria will gather more to the top for air.