Minimally processed forms of calcium carbonate are allowed such as dolomitic lime and oyster shell flour. However, most pH buffering materials are synthetic, and at this time most producers consider them necessary to achieve a steady and balanced pH without causing stress for fish and the system as a whole. CNG allows these synthetic materials (such as calcium hydroxide, potassium hydroxide, and others), at least until further developments in the field of aquaponics yields a more natural alternative.