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It’s remarkable what a bit of TLC can do, especially when you’re a little cleaner fish with a potentially dangerous client.
 
Down in the busy world of the coral reef, cleaner fish earn their living by removing and eating the parasites off other fish, cleverly providing a much-needed grooming service in exchange for a tasty meal. But sometimes giving that little bit of extra attention can pay huge dividends, as scientists have shown that cleaners who upgrade their service by gently caressing their clients with their fins benefit from calmer, more cooperative clients.
 
This is especially helpful if the customer is a predator that could attack the cleaner, but it seems that the cleaner fish’s touch makes normally aggressive hunters so calm that it transforms the cleaning station into a safe haven for any other fish in the area.
 
Scientists have often marvelled at how prey fish seem so relaxed and non-vigilant at cleaning stations, even with lots of predators around. A cleaning station should in theory be a marvellous place for hunters to strike, but it never seems to happen. So in order to determine what was actually happening, scientists from the University of Queensland in Brisbane built mini coral-reefs in aquaria and watched the interactions between cleaners, their predatory clients and other potential prey species in the area.
 
They found that predators in aquaria with cleaners chased prey two thirds less often than those in aquaria without a cleaner fish, and their aggression was reduced even when they weren’t actively being groomed. The number of chases also decreased the longer a cleaner spent touching a predator with its fins. So in the coral reef world at least, it seems that all it takes to keep a bully in check and bystanders safe is good service and a gentle rub...