Cleaner shrimp are carnivorous invertebrates, meaning that their diet consists of meaty marine foods. The mucous is so important that it is even believed to be part of what drives certain cleaner species to preferentially choose certain individuals or species to clean. But you should not rely on the cleaning behavior alone to meet their full nutritional needs alone. Feed them routinely with prepared frozen foods, flakes, and pellets to ensure they get an adequate amount of calories and nutrition.