Dippel's oil, a nitrogenous by-product of the dry distillation manufacture of bone char
Denitrifying bacteria form a necessary part of the process known as denitrification as part of the nitrogen cycle, their primary purpose being to metabolise nitrogenous compounds, with the assistance of the nitrate reductase enzyme, to turn oxides back to nitrogen gas or nitrous oxides for energy generation.
If desired, pothos, java fern, java moss, or other semiaquatic plants can be placed in the pot to help absorb nitrogenous waste produced by the newts.