There are several synonyms for the word "fish tank," which is a container used for keeping fish and aquatic plants. The most common synonyms for fish tank include aquarium, fish bowl, fishpond, and fishtank. Aquarium is a large and fully enclosed water tank with a filtration system that provides clean and healthy water for fish. A fish bowl is a small glass container, which is often used for keeping a single fish. A fishpond is a bigger and outdoor system that can house more fish and aquatic plants. Finally, fishtank is a more casual and less formal way of referring to fish tanks. Whether you're a beginner or an expert, there's a fish tank that suits your needs.