f) Wash fractions containing healthy larvae into a measuring cylinder.
g) Take sub-samples as described before and determine the total number surviving. Measure a sample of 50 to 100 and calculate mean shell length.
Note: The addition of a few drops of formalin (10% formaldehyde solution, neutralized over calcium carbonate in the form of limestone or marble chips) will immobilize the larvae. Discard the counted sample(s).
h) Return the larvae to the culture tank and restore the aeration.
i) Repeat this procedure at 48-hour intervals.