They do scavenge but I think they might need some feeding too. They will eat anything from flakes to frozen. I use a turkey baster to squirt the food in so I can direct some at the shyer creatures. My Caribbean cleaner shrimp are so rowdy they run up to compete with the fish, but my peppermints and fire shrimp stay in their little caves and crevices, so I have to make sure some food gets to them.