In dry form it has an unlimited shelf life Bacterial contains nitrifying bacterial cultures in lyophilized form. If a pack of Bacterial of 50 ml will be added to pond water, within 24 hours over 20 thousand million mainly nitrifying bacteria will be produced. Although they are very small in size, and invisible for the human eye, these bacteria are indispensable for nearly any form of life on earth. This also applies for our garden ponds