A new study has shown that cleaner fish are coloured and patterned with a kind of uniform to stop them being eaten by the fish that they are cleaning.

Cleaner fish hang out at reefs, where larger fish stop by and allow them to pick off parasites. The cleaner fish eat the parasites and the larger fish get a clean. But scientists wondered what stops the cleaner fish becoming a snack themselves.

Researchers from the University of Queensland in Australia have worked out that it’s the colours and patterns of the fish that sets them apart –as though they’re wearing a uniform.

There are lots of different species of fish that act as cleaners – wrasse, gobies, and cleaner shrimps, to name a few. The scientists noticed that many of these species have a dark stripe along their side, with blue or yellow colouring.

Check out the picture in this article: the fish with the blue strip is a cleaner wrasse. It is about to help clean the other fish.

The researchers believe the stripes and colouring act as a signal to the larger fish not to eat the cleaner as the cleaners often go inside the larger fish's mouth to clean in there too!

The researchers believe that a wrasse's stripes and colouring ensure it doesn't get eaten by bigger fish. Which is a good thing since wrasse often go inside a fish's mouth!

Watch this video to see some cleaner wrasse fish in action!