In response to public comments, we updated the standards to allow for soil, compost, and vermicompost to be used in dead-end or non-recirculating sections of the system. These materials are natural, non-synthetic sources of nutrients. Many aquaponics systems function perfectly well without the use of these materials, but some producers find soil, compost, and vermicompost useful. CNG’s revised AP standards will allow their use in CNG operations, as long as the water does not recirculate from the portion of the system where those materials are used.