One of the challenges with Japanese eel (Anguilla japonica) seedling production is the slow growth of leptocephali. This issue arises from a fundamental problem with the current methods for raising leptocephali. In essence, the balance between the amount of energy obtained from feeding and kinetic energy significantly differs from that in the natural environment. This slow growth results in a reduced size of metamorphosable leptocephalus and ultimately leads to smaller artificial glass eels. We hypothesize that this reduction in the size of artificial glass eels may be attributed to time-related stress during rearing. Therefore, we propose the "time-over theory" based on a series of phenomena.