A lаbоrаtоry is аttempting tо standardize a protocol to hatch Aedes aegypti eggs. They submerged 1,000 eggs in deionized (DI) water. After 1 hour, only 1% of the eggs had hatched. The hatching rate and synchronization were considered unsatisfactory. The team proposed several modifications to increase overall hatch rate and improve hatching synchrony. Which of the following modification(s) would most likely improve the outcome?