NPT - natural planted tank
Broad term for soil based aquariums.
Many are trying to tie the use of this term to the works of Dianna Walstad author of Ecology of the Planted Aquarium.
The author herself doesn't claim this if any bother to actually read her book.
Others have tied it to only low light or natural light, no CO2 systems with an emphasis on low-tech, natural aquariums and aquatic plants.
(lack of techy stuff)
I like this web posted description that's from a site dedicated to the topic:
The term "Natural Aquarium" can be used to describe different types of planted aquariums, including any planted aquarium
. To me a natural aquarium is a low tech planted tank, generally set up to resemble natural types of settings. These tanks are usually a bit less formal than some of the other planted tank styles, and can often include invertebrates as well as fish and plants. I think of a natural aquarium as compared to other aquariums as a country garden is to a more formal one.
To me NPT is the use of dirt as the primary media under a containing cap material.
Google it and you spend the rest of the day reading the results.