There are several caterpillar species that feed on the lettuce plants. Only organic pesticides can be used and they should be specific to the insect. There is the possibility that the pesticide will wash off the leaves and into the culture system water and harm the fish. Bacillus thuringiensis, available in many commercial formulations, can be used. It is specific to caterpillars. The wettable powder is applied twice each week on all the plants in the system.
An insect-attracting "bug zapper" light is turned on each night to attract night flying moths. Grassy areas surrounding the system are cut frequently to reduce habitat for moths.