The bulldozer of the freshwater world. This fish was a mistake. It is a large, heavy-bodied creature capable of reaching over 60 centimetres in length and weighing more than 5 kilograms. The colour varies wildly: orange, white, black, gold, spotted, or blotched. These variations exist because they are descended from ornamental pond fish. But the behaviour remains the same regardless of colour. It is destructive. A pretty fish that causes ugly problems. Ecosystem wreckers possess a single, devastating habit. Koi carp feed by grubbing through the bottom mud, sucking up worms, insect larvae and anything else they can find. But they do not just eat. They dig. They root through the sediment like a herd of pigs, stirring up clouds of mud, uprooting aquatic plants and destroying the habitat for native fish and insects. A single carp can turn a clear lake into a muddy mess in a single season. It ruins its own home. It is the poster child for why aquarium fish should never be released into the wild. Someone thought they were being kind, letting their pet go free. Now there is a multi-million dollar problem. Teams of people try to trap, net and electrocute these fish out of the waterways. Good intentions. Bad outcomes. It is a familiar story. To catch a koi carp is to catch a villain. The fish looks like a garden ornament but acts like a wrecking ball. There is no Māori name because it is not a native fish. It came from Asia, via the garden pond. The origin is domestic. The result is chaotic. Today it is the fish of the polluted river, the one that thrives where nothing else can live, turning the water brown and the ecosystem upside down. The lake is murky. The carp roots in the mud, stirring up clouds, eating everything. The native fish are gone. The carp does not care. It has no interest in the balance it disrupted. It just eats. That is what it does. The water stays brown.