I first became fascinated with this concept when I read a Tropical Fish Hobbiest article about a NPT fish room. I then had to buy the book, boy it's a text book, rather than a fish book. Lots of science in there. If you like reading a biology text book, this book is for you. Otherwise it's still a good read, and you'll learn a ton, but it'll feel a little like work.

Basic premises of the Dr. Walstad Method.

-Soil substrate contains 7 different bacterias that can live in aquariums.
-Soil substrate provides co2 to the aquarium from decomposing matter.
-Plants when given the opportunity prefer to feed on ammonia.
-All nutrients that plants need can be provided from fish food.
-Nutrients are removed from the aquarium via plant trimming.
-Water changes are not necessary.
-Topping off water, does not change hardness or ph after the tank is established.
-Filtration should not be used.
-Circulation is an option.

So basically we see here, a tank that never needs a water change, doesn't need a filter. Sounds too good to be true right? That's what I thought also, until I started reading her forum and seeing amazing tanks, following these exact guidelines.

Have a look at this tank. It won't knock your socks off, until you realize there is no filtration, no fertilizers, and no water changes, and it's been stable for 9+ years.