The only problem with reading Diana Walstad's material is how involved it can quickly get and it is far riskier than my method, which by the way I have used in setting up dozens of tanks. I do not recommend Walstad for anyone not well versed in more simple methods. Using soil is fraught with complications if you don't know exactly what you are doing.
I agree with lightly stocking, and sufficient plants. But it does work. Ammonia and nitrite will be zero, and it can't get much safer for fish than that.
Byron Hosking, BMus, MA
Vancouver, BC, Canada
Something we all need to remember: The fish you've acquired was quite happy not being owned by you, minding its own business. If you’re going to take it under your wing then you’re responsible for it. Every aspect of its life is under your control, from water quality and temperature to swimming space. [Nathan Hill in PFK]