Leonardite?

[water_wako]

I saw this blog on the Internet of some one setting up a planted tank. They used Leonardite under the substrate. It is also called Diamond Black. Is it wise to use this? Would it be also wise to use the other two products as well: Diamond Nectar and Rare Earth?

Here's a link. Just scroll down: http://www.canadianwholesalehydroponics.com/products.cfm?cat_id=55&show_products=1&catpage=1