Many crustaceans such as shrimp mainly eat dead animals and scraps they find. They are considered scavengers that search for their food.
What a crustacean eats depends on its size and what species it is. Most crustaceans hunt for food at night. They spend their days hiding in small places to avoid being eaten themselves.
Shrimp and crab scavenge for food that is floating around the sea. Larger crabs and lobsters will attack prey by squeezing them with their claws. Smaller crustaceans such as barnacles use the hair on their legs to capture tiny creatures that pass by them in the water