Deniballs are manufactured from a unique biologically based plastic. One to three packages of 0.8 litres (app. 0.2 gal) is enough to supply the Nitratereductor as the sole food source for 12 months. For the Nitratereductor NR 5000, about 5 litres (1.3 gallons) are required. Changing the Deniballs after approximately 12 months is recommended to ensure safe and maintenance free denitrification in fresh- and saltwater aquaria.