Shallow wooden trays were constructed, lined with plastic, and filled with water. Lettuce plantlets were placed in small “net pots” inserted in holes in styrofoam panels suspended over the water by resting their edges on the walls of the trays. The lettuce roots took up nutrients from the water in the trays. The nutrients were provided either by added chemical fertilizers or by effluent water taken from tanks in which fish were grown (plus some supplemental chemical nutrients added). The water from the lettuce trays was recycled to the fish tanks each time fish-culture effluent water was added to the trays.