The term TANK OCCUPANT can be summarized as a person who resides in a tank. This could refer to a variety of occupations, such as a soldier, a marine biologist, or an aquarist. The crossword solution for this term is TETRA, which is a type of tropical fish that is often kept in tanks. Therefore, the term TANK OCCUPANT could refer to someone who is responsible for caring for and maintaining a tank full of tetras.