India, April 26 -- T he Pleco family of fish are covered in rows of spiky armour, and can suck algae off rock. Many species can drag themselves out of water and "walk" on land with the help of their spines and fins. Native to South America, they are now found in water bodies around the world. It turned out they were useful in aquarium tanks, as a way to keep the water clean. And so they were bred, shipped around the world and spread. But they grow fast, and can reach 1.5 ft in length. When they grow too big for a tank, they are often released into a local water body or flushed into sewers. Out in the wild, this family of fish - made up of species such as suckermouth catfish, armoured sailfin catfish and vermiculated sailfin catfish - can wr...