Abstract <p>Cleaning mutualism is a key interaction between marine fishes, although there are estuarine and even freshwater cleaners. The silver batfish <i>Monodactylus argenteus</i> is an estuarine facultative cleaner that cleans only as juvenile. I summarise herein observations on cleaning activity of the silver batfish over five years at a location in an Australian estuary. The cleaning activity of this fish at the observed estuary typically lasts from January to April–May. Based on the cleaning activity by the silver batfish at the estuary for a defined period of the year I propose a novel concept among cleaning fish, that of a periodic cleaner (i. e. occurring at somewhat regular intervals from one year to another). I also suggest that this concept may apply to additional estuarine cleaners, as estuaries are among the least studied environments known to harbour cleaning fish.</p>