Maybe just to set your expectations right, the cleaner shrimps is neither a prevention nor cure for white spots or parasite-related diseases. Even if it does reduce some likelihood of the diseases, it will be moot once they start feeding. Like many other lifestock, once they are trained to eat prepared foods, they lose their 'instinct' and stop hunting, in this case, cleaning.
Nevertheless, cleaner shrimp is also a good clean up crew if you don't mind their voracious apetite because they eat almost anything, so can help you scavenge your rocks/sandbed.