May be in the nature of live microorganisms. Or characteristics of the feed water with culture medium. When the food runs out Jersey to microbial degradation. Therefore need to use it within 1-4 weeks.
May be in the nature of live microorganisms or characteristics of water reared Petri dishes. When the food runs out, the performance capacity atrophy to little rush County, within 1-4 weeks.
It may be in the form of organisms live or the characteristics of the water, cultivated bacteria feast on food directory statoliths were empty capacity will decline in the efficiency and therefore must get used up within 1 - 4 weeks