Freshwater crustaceans such as shrimp, crabs, and crayfish can provide many benefits to a freshwater aquarium. They are excellent cleaners, scavenging for leftover food and debris, and can help control algae growth. Additionally, they can add visual interest to the aquarium with their unique shapes and vibrant colors. Some species can even serve as food for larger fish, providing a natural source of nutrition. Overall, incorporating crustaceans into a freshwater aquarium can contribute to a healthy and balanced ecosystem.