Unfortunately I feel very strongly about cleaner wrasses in captivity, and I say "unfortunately" because it's really too bad I love that fish! If you've ever seen Hawaiian cleaner wrasses they will take your breath away. But not only do cleaner wrasses fare poorly in captivity, it's a double edged sword because it means a cleaner station was "taken offline" so to speak in the wild and this probably does more harm than we can imagine. In the case of cleaner shrimp this is probably true to a lesser extent but it's also mitigated by the fact that cleaner shrimp have millions of babies every couple of weeks so for every adult removed from the wild it means one more of the millions that might not have survived now gets a chance to take their place instead. Cleaner wrasses on the other hand spawn less frequently and the cleaner stations will only have 2 or 3 of these fish and once they're gone they're gone. It sucks, but if we have any love or respect of the reef at all we have to be disciplined and leave cleaner wrasses in the wild, some species we have to draw the line on and say "not in my tank" even if it means we lose out on value inside our own captive reef.
As for cleaners vs ich, I would venture that there is still some value even if they do nothing to the ich life cycle itself. When I see a fish with ich it very often tries to scratch against different surfaces and this risks injury or lessens the slime coat which in turn opens the door for escalation. Whereas cleaner shrimp do their thing and it must feel good since a fish who recognizes what a cleaner does will seek it out and I suspect it's a little more surgical than random rock scraping. Sort of like how a hot bath doesn't cure a cold or the sniffles but you feel better anyhow after one and any little bit helps.
Just my thoughts based on maybe nothing in particular, thanks for listening
