The five species of cleaner wrasses of the genus Labroides are truly an interesting group of fish. While not a unique behavior in the underwater world, their pathogenic cleaning service is quite remarkable.
The typical cleaner wrasse makes its living by nibbling parasites off other fish. A wrasse hangs out at an established “station” on a reef that other fish visit for cleaning. By eating the parasites, the wrasse gets a meal and the client gets a clean bill of health. Everyone leaves happy!
The wrasses in their ‘stations’ clean parasites, dead and damaged scales, and mucus from bony fishes, sharks, and sea turtles that present themselves for cleaning. A number of scientific studies and research attest to the important role these fish play in the health of the reefs. The overall health, size, and even diversity of fishes is greater in the reefs where cleaner wrasses are found versus those without their services.
Where cleaner wrasses are absent, resident fishes were 37% less abundant and 23% less species rich per reef, compared to control reefs, juveniles of visitors (fish likely to move between reefs) were 65% less abundant on removal reefs suggesting cleaners may also affect recruitment. This may, in part, explain the 23% lower abundance and 33% lower species richness of visitor fishes, and 66% lower abundance of visitor herbivores (Acanthuridae) on removal reefs that were also observed. ( Waldie PA, Blomberg SP, Cheney KL, Goldizen AW, Grutter AS (2011) Long-Term Effects of the Cleaner Fish Labroides dimidiatus on Coral Reef Fish Communities.)
This beneficial behavior is continued in captivity as well. While not to be completely relied upon over quarantine and proper conditioning, wrasse cleaning services can and does help in keeping other fishes healthy in our care. Numerous benefits from cleaner fish services have been documented, besides the obvious upside of removing parasites.
Cleaner fish also remove dead and damaged scales which are easy attachment points for some pathogens, stimulating mucus production, the first line of fish immune system defense, as well as the therapeutic affect of “it just feels good” much like we humans enjoy a back rub. The other fish benefiting from these services can be seen in dealer’s tanks when a new cleaner wrasse is added, fish will literally line up to await this service.
Cleaner wrasses are by no means an easy fish, but in the proper circumstances can be well cared for relatively easily, in some cases living over 10 years in captivity. Much of their perceived difficulty is related to the fact that they are obligate cleaners. Cleaning behavior can be classified two ways: facultative cleaning and obligate cleaning. Facultative cleaners provide this service on occasion or perhaps during a limited stage in it’s life but then stops as it grows. Juvenile angelfish, butterflyfish and many wrasses for example example, as young fish they provide this fish cleaning service, but prefer other food sources and stop entirely as adults.
Obligate cleaners need, or are obligated, to clean as nearly all of their nutrition is met this way. Another reason for their perceived difficulty exists simply because of the service that they provide. Hobbyists may add cleaners in tanks with fish suffering from terrible disease, often ich or marine velvet, as a solution. However, such conditions would be fatal to just about any fish, even perceived hardy fish – cleaner wrasses.
That is not to say that if any tank is cycled and healthy a cleaner wrasse would be an appropriate choice, but rather in the proper setting these wonderful fish can be a beneficial addition. But what is the proper setting? Remember, they need to get much of their nutrition through cleaning client fish.
Captive bred cleaner wrasses such as these may one day be able to supply the demand from the aquarium hobby. In the wild they may clean hundreds, in some exceptional cases, thousands of fish a day. Most home aquariums come nowhere near these numbers, and if there are too few fish a cleaner wrasse can make a pest of itself in trying to force it’s service on unwilling participants.
In the obligate success stories the tank was usually a larger system, 150g or more and was heavily stocked with large fishes. The bigger the tank and the more potential clients the better. And while quarantine is best practice for any fish in aquarist care, cleaner wrasses most definitely contribute to the overall good health and well-being to fish in an appropriately sized setting.
The behavior of these unique fish is truly something to marvel at, and as a community that enjoys the natural aquatic world we as hobbyists want to afford these magnificent creatures the dignity they deserve and only add them where we are able to meet their specific needs.