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.
These small, busy fish set up ‘stations’ in a part of the reef, in which a pair or harem diligently 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 healthyin 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.
Despite the valuable service these fish can provide in aquaria many in the hobby make the strong cry that these fish should not be collected and kept in home aquariums. In most cases two reasons are given. 1) Cleaner wrasses are very important to the overall health of the reef and should not be removed, lest more reefs see this sort of demise.Opponents to their collection will cite the previously mentioned study in which they were removed from the reef for 8.5 years and compared to reef where they were not removed and the decline to the reef was significant. 2) the dismal survival record of cleaner wrasses in captivity. Both of those concerns will be addressed here.
To determine if removing cleaner wrasses for aquarium collection presents a problem for other fishes on the reef a look at the research done on reef recruitment of juvenile Labroides needs to be considered. The same group of scientists the next year noticed that the recruitment of juvenile cleaners was negatively affected by the presence of established adult cleaners. Meaning that if there were enough Labroides already there the juveniles that tried to settle would be driven off.
This makes sense because a cleaning station is in essence, a territory for resources. The established cleaner wrasse will, in most cases, chase the new cleaner out of it’s territory. This is a behavior which most aquarists have observed in just about any territorial fish. An interloper is competition for limited resources.
In some cases the new fish can move on and establish a territory of it’s own, but in most cases this is not possible as resources are not abundant enough to support a new station. And even though cleaners often get a ‘free pass’ from predators, this is not always the case, especially for a cleaner without a cleaning station.
The second reason given is the poor survival record of Labroides in aquaria. 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. Because of this ‘need to clean’ many Labroides that make their way into the LFS don’t, and never will, take prepared foods.
Another reason for their perceived difficulty exists simply because of the service that they provide. On numerous occasions I have walked into a store that sells saltwater fish (I am not referring to LFS in these cases) in which a new hobbyist is telling a clerk/salesperson about a terrible disease that is ravaging their tank, often ich or marine velvet, and are told about ‘the miracle solution’ cleaner wrasse. Sadly, the unwitting customer makes the purchase and adds the cleaner wrasse to a tank with conditions that would be fatal to just about any fish, even perceived hardy fish.
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.
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. However, I have personally witnessed many cases of success with cleaner wrasses.
In these 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 were we able to meet their specific needs.
This is a guest contribution by TJ Engels, one of the marine fish specialists at Greenwich Aquaria.