The diet of cleaner wrasses is 75% gnathid isopods, the rest being scales and fish mucus that comes off with the isopods. So if you have a problem with those pests, the wrasse would be a good option.
By the way, in all my years in this hobby/industry, I have only heard of one case of someone having trouble this those isopods. The cirolanid isopods that seem to be going around now are a different animal.