“Fish Flashing:” Fishy Therapy, or Simply a Good Backscratch?

I was watching these French angels during a dive at Bonaire when the nearer one turned on its side and began rubbing against the rubble on the sandy bottom, something like my dog scratching her back on the carpet. The other one looks, in the photo, like it may have been doing the same thing, but I was so taken by surprise at the time, I’m not sure whether it was.

WHETHER FOR HEALTH OR PLEASURE, FISH SOMETIMES ENGAGE IN A PHENOMENON CALLED “FLASHING,” otherwise known as rubbingtheir bodies along the sea bottom.

Ned Deloach, in his estimable Reef Fish Behavior, describes it as an effort to deal with the irritation of parasites by scrapping them off, an alternative to the much more commonly seen symbiotic cleaning by small fishes and crustaceans.

Discussions about the cleaning dynamic sometimes suggest that, in addition to health benefits, the fish derive a pleasurable “tingly” sensation from a good cleaning and I’ve read somewhere that seafloor rubbing may do that.


Maddeningly, I can’t find it. If you google “fish flashing” you get a lot of sites for home aquarium enthusiasts, where questions mostly yield answers about parasites, disease or, otherwise, a problem with the tank’s water.

A few suggest the backscratch possibility, but the answer most likely is that it’s to deal some physical issue.

On the other hand, I found this great video.  And the little guy seems to be having a terrific time. I’m generally opposed to messing with sea life, but I’m envious of this one.

Please click on this screenshot to view the video.

PRINCIPAL SOURCE: Reef Fish Behavior, Ned DeLoach