Some of the clay based substrates like Laterite are very good for plants, but they can be messy. Since they're basically compressed dirt, they're almost impossible to clean using the traditional bucket method. Besides, when you do clean them, you lose some of the clay. My solution to the problem is laziness. In an aquarium with under gravel filtering, I just dumped some of the stuff directly from its plastic bag onto the gravel substrate. The water cleared in a couple three hours. No mess. No work.
more posts...