The Gyeonggi Province Agricultural Technology Institute has produced and published a "Lettuce Environmentally Friendly Management Manual for Aquaponics" to spread environmentally friendly circular agriculture technology. Aquaponics is a circular environmentally friendly agricultural system that combines fish farming and hydroponics, using fish excrement to grow plants and returning the purified water back to the fish. Fish excrement is converted into plant nutrients such as nitrates by bacteria, and the plants absorb these nutrients while purifying the water, which is then returned to the fish tank. It is environmentally friendly as it reuses water by up to 95-99% and uses little water, and almost no chemical fertilizers or pesticides. The manual is composed to suit the field, from sowing to environmentally friendly pest control, including: the concept and principle of aquaponics, lettuce seedling and planting management, nutrient management and physiological disorder response ...