Cleaning Stations: How to Watch the Reef’s Car Wash

6 min read By ScubaSnap

Big fish queue up to have small cleaners pick off their parasites. How cleaning stations work, why cleaners sometimes cheat, and how divers can watch without disrupting them.

A big fish hangs motionless with its mouth open while a small striped fish swims in and out between its teeth. Neither one eats the other. You have found a cleaning station, one of the busiest services on the reef, and also one of the easiest for divers to interrupt without noticing.

What a cleaning station is

A cleaning station is a fixed spot on the reef where small cleaners pick parasites off bigger fish. The best-known cleaner is the bluestreak cleaner wrasse (Labroides dimidiatus). FishBase says it stays at stations where other fish come to be cleaned, and feeds on crustacean parasites and on the mucus of other fish. A station is held by a pair of adults, a group of juveniles, or a group of females with one dominant male. FishBase also notes that it greets an unfamiliar visitor with a dance, moving the back part of its body up and down, and that juveniles do this when divers come close.

Shrimps run stations too. SeaLifeBase describes the Banded Coral Shrimp as a cleaner that removes parasites, injured tissue and leftover food from reef fish. Pederson's Cleaner Shrimp lives with sea anemones and cleans fish at its anemone.

Cleaners really do clean

For a long time scientists were not sure the clients gained anything, because studies had failed to show any benefit. A 1999 study in Nature by Lexa Grutter settled it on the Great Barrier Reef: the cleaner wrasse cut the parasites on its client, the thicklip wrasse, with a 4.5-fold difference within 12 hours. Cleaning is good for both sides.

It matters for the whole reef, too. In a 2003 study in Current Biology, Grutter, Murphy and Choat kept cleaner wrasse away from small reefs for 18 months. Those reefs ended up with half the fish species and a quarter of the fish. Only fish that move between reefs were affected: they seem to choose reefs with a cleaner.

Honest cleaners and cheats

Cleaning has its own politics. A cleaner wrasse would rather eat a client's mucus than its parasites, so it is tempted to cheat. In a 2006 study in Nature, Bshary and Grutter found that client fish watch how a cleaner treats others, and that cleaners behave better when a watching client is nearby. Reputation counts, even for a fish.

Then there are the real fraudsters. The false cleanerfish (Aspidontus taeniatus), a blenny, looks and even moves like the cleaner wrasse, FishBase says. Fish that let it close get bitten: it takes scales, mucus and bits of fin, then darts back into the coral. The giveaway is the mouth, which sits under the snout in the blenny and at the tip of the snout in the real cleaner. Experienced fish learn to recognise it and often chase it off.

What divers do to a cleaning station

A 2015 study in PLOS ONE (Titus, Daly and Exton) watched Pederson's Cleaner Shrimp stations in Honduras. Even on a reef visited by divers for decades, cleaning dropped by more than half when divers were present. On a reef that divers never visit, cleaning was suppressed even when divers were more than 10 metres from the station. The authors concluded that reef fish never fully get used to divers.

Manta rays use cleaning stations too. A 2018 study for The Manta Trust and the University of York (Pelletier) found divers had little impact on reef mantas at Maldives cleaning stations, and that mantas most often showed no reaction when divers stayed more than 3 metres away and kept off the station itself.

Cleaning stations on ScubaSnap

Divers have uploaded pictures of these cleaners and clients:

  • Banded Coral Shrimp: red and white bands and long white antennae, in the Indo-Pacific and the western Atlantic, living in crevices and under overhangs (SeaLifeBase).
  • Pederson's Cleaner Shrimp: western Atlantic, always living with a sea anemone. The shrimp from the 2015 diver study.
  • Spotted Cleaner Shrimp: a small western Atlantic shrimp, up to about 2.5 centimetres, that lives with sea anemones from the Florida Keys to Venezuela (SeaLifeBase).
  • Thicklip Wrasse: the client fish in the 1999 study.
  • Emperor Angelfish: FishBase notes that young and adults may clean much larger fish, and the Australian Museum says juveniles are often seen under ledges near cleaner shrimps.

No one has uploaded a bluestreak cleaner wrasse yet: if you photograph one, the AI fish identifier will add it. Our directory lists several stations by name: Cleaning Station in Sabah, Malaysia, Gangehi North Kandu manta cleaning station in the Maldives, and the old and new Mill Channel cleaning stations in Yap.

Watching without jamming it

Do not put your hand into a cleaning station or offer it to a cleaner shrimp. Green Fins asks divers never to touch or handle marine life, and every minute a cleaner spends on you is a minute it is not cleaning fish.

  • Keep your distance. The research shows that divers suppress cleaning even from several metres away. Watch from a distance, keep it brief, and move on.
  • Stay off the station. For mantas, stay more than 3 metres away and never settle on the station itself.
  • Keep still and neutral. Do not block the way in for waiting fish, and do not kick up sand. Our eight habits of reef etiquette cover buoyancy and finning.
  • Go easy with the strobe. Green Fins advises limiting strong lights and flashes, which stress marine life.

The short version

  • Cleaner wrasse and cleaner shrimp remove parasites at fixed stations
  • Cleaning clearly helps the clients, and reefs without cleaners hold fewer fish
  • Cleaners can cheat, but they behave better when other fish are watching
  • A blenny copies the cleaner wrasse to bite fish; look at the mouth
  • Divers reduce cleaning even from several metres away: watch briefly, from a distance

Sources and further reading