The term 'fishtank' is often used interchangeably with the word 'AQUARIUM', which is an 8-letter word. An AQUARIUM is a tank or container that holds water and is used to keep aquatic animals, plants, and other organisms. Aquariums can be used for both decorative and educational purposes, and they can range in size from small bowls to large tanks. They are often found in homes, schools, and public places such as zoos and aquariums.