From what I have read about the walstad method and the scientific concepts behind it I believe you will be fine as long as you set it up properly. I am no expert by any means and would never claim to be one even if I had a phd. I am, however, a fisheries biology major in college. The walstad method relies on the same basic biochemical processes as found in nature. The whole point of an over planted natural tank is to mimic nature. We, however, as hobbyists can't fully mimic all of the growing and living biological organisms and nitrogen "fixers" and wouldn't want to. Most of the nitrogen fixation is done by Cyanobacteria and green algae. Who wants green algae bloomed water in their tank. On the flip side of the hobby, many reef tanks incorporate a refugium where algae growth is encouraged for this very reason. This is a concept that the walstad method and aquaponics enthusiasts use to they advantage. Most plants can't take up the free nitrogen or ammonia (NH3 and NH4) but nitrifying bacteria can and does and it produces a form of nitrogen that the plants can use. There are full scale aquaponic farms in Australia that never have to do water changes because the plants take up all of the nitrates and nitrites. From what I have gathered about walstad's method of planting a tank it is nothing more than a submerged aquaponic system. In short, so long as you set up the tank in the method described by Dr. Walstad than not only should you be fine but you have a low maintance beautifully planted tank.
Last edited by bigbassbob; 01-12-2013 at 05:28 AM.
Reason: Grammar errors. And additions.