Diana Walstad did write the Ecology of the Planted Aquarium. The subject of the book is how plants, fish, aerobic and anaerobic bacteria all interact to produce the observed changes in water chemistry. The book then goes on to describe how to set up a tank with no mechanical filtration in it and use plants as the filter. In theory, when it is set up right, you add your plants and fish all at once in a brand new uncycled tank. The balance between fast growing plants and fish waste production keeps the fish and the plants healthy. I have not gone quite that far so far but I do have a couple of Walstad type tanks set up and they do grow plants well while keeping my fish healthy. In my case I have a sponge filter that I properly cycled before putting the fish in so I don't know that it would be OK to do it completely the way she suggested. Contrary to what people often worry about with anaerobic bacteria, she cites information that the anaerobic bacteria in the root zone of plants helps the plants obtain needed nutrients. If you choose to go in the direction of an El Natural tank, do your homework first or expect the scanty information available about it on line to get you into trouble.
