Every year, young Cuban entrepreneurs Jose Martinez and Joel Lopez cultivate 12 tonnes of tilapia in their ponds using 'aquaponics,' an aquaculture system that allows them to sell fresh fish to the inhabitants of an island where, paradoxically, this food is scarce. In aquaponics, farmed fish wastewater becomes a vital nutrient source for hydroponically cultivated plants, like lettuce, playing a crucial role in water purification. IMAGES AND SOUNDBITES