Arimo is a city in the Marsh Valley in central Bannock County, Idaho, United States, that is part of the 'Pocatello Metropolitan Statistical Ar…Arimo is a city in the Marsh Valley in central Bannock County, Idaho, United States, that is part of the 'Pocatello Metropolitan Statistical Area'. The population was 354 at the 2020 census. According to the United States Census Bureau, the city has a total area of 0.44 square miles, all of it land.