In overpopulated tanks, it becomes difficult to maintain healthful water parameters; metabolic waste (excrement) accumulates rapidly, even when a highly efficient filter is employed.
It ends with the fantastically overpopulated alternate timeline sending someone back to assassinate the title character, allowing darkness to fall for thankful billions.
The program operates specially-designed trucks that transport adoptable dogs from areas that are overpopulated to partner shelters where adoptable animals are in demand.