We should avoid buying cleaner wrasses simply for the impact that collection of these fish has on the reef. The simple collection of cleaner wrasses from the reef reduces the overall fish population.
Here's an excerpt from this page:
http://www.ornamental-fish-int.org/d...11495&gid=4838
A recent study which analysed the causal link between cleaner fish presence/absence and reef fish diversity at Ras Mohammed, Egypt, demonstrated that Labroides dimidiatus have a significant effect on local reef fish diversity with a more rapid increase in diversity being recorded when cleaner fish are added to individual reef patches [46]. Indeed, the removal of Labroides dimidiatus had no effects on fish abundance within the first few weeks, but a significant decline in fish diversity was recorded after a 4-20 month time period. On the other hand, the immigration or addition of Labroides dimidiatus individuals to reef patches led to an immediate, i.e. within 2-4 weeks, significant increase in fish diversity.
In addition to playing a key role in reef health - and thus the removal of Labroides dimidiatus in large quantities for the aquarium trade potentially having negative impacts on reef diversity - aquarists are advised to avoid this species as it tends to fare poorly in aquarium conditions unless kept with a large community of fishes, and is not likely to accept substitute foods [47].
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The other problem is that cleaner wrasses are obligate eaters. In other words, they live almost entirely on what they can clean off other fish. Once our other fish have a greatly reduced population of parasites for them to feed on, they starve to death. Much like a mandarin in too small of a tank.
A much better option for a cleaner is a cleaner shrimp. They clean, and they eat food.