It eats everything green. Every weed every submerged plant every bit of vegetation that holds the ecosystem together. The grass carp does not discriminate. It consumes aquatic plants at a rate that can strip a lake bare in a single season. What was once a complex habitat becomes an empty bowl of water. Introduced to New Zealand in the 1960s for weed control, the grass carp has become one of the most destructive invasive fish species in the country. Native to eastern Asia, this large cyprinid reaches up to 1.5 metres in length and can weigh over 40 kilograms. Its massive size and insatiable appetite make it a formidable force in any waterway it enters. The fish inhabits lakes ponds and slow-flowing rivers where aquatic vegetation grows thickly. It prefers warm shallow waters with dense plant growth, though it will venture into deeper areas if food is scarce. Unlike native herbivores that feed selectively, the grass carp consumes entire plants root and stem leaving nothing behind. Spawning occurs in flowing water during spring and summer. Eggs are released into the current where they drift downstream hatching in warm temperatures. In New Zealand most grass carp are sterile triploids introduced specifically for weed control without establishing breeding populations. However fertile diploid individuals have been found raising concerns about uncontrolled reproduction. Diet consists almost entirely of aquatic vegetation. The fish can consume up to three times its body weight in plants daily. This feeding behaviour destroys habitat for native fish birds and invertebrates that depend on aquatic plants for shelter and food. Water quality deteriorates as sediment is stirred up and nutrients are released from decaying plant matter. Classified as Introduced the grass carp faces strict controls in New Zealand. Sterile triploid individuals are occasionally used for targeted weed control under permit but wild populations are actively managed through removal programmes. The threat to native ecosystems is severe. Lakes stripped of vegetation lose their ability to support diverse life. Conservation efforts focus on preventing further introductions and removing established populations before they spread.