I have wrote a few comments regarding the kleins, Mine ate all my aiptasia within 2 weeks, and I did notice him nipping at my xenia, only the tips, and never enough to cause harm or reduction in xenia. He left everything else alone, he did eat like a pig and I would recommend feeding him atleast 3 times a day. I would be leary as they are known to eat clams and other invertebrates, and once they have a taste of it(clam) I heard they will never shake it. People have said they will destroy some feather dusters so I pulled my larger ones out for my refgium, however I had some smaller ones that I didn't move and he left them alone. He did an amazing job at cleaning up the aiptasia, and I would highly recomend him for this purpose, but for the clam and other anemone, they might need protection against him IMO.
most anything that effectively clears the aiptasia population is more than likely gonna bash on somehting else in the reef.
This fish was recommended to me by a few other members, neither had anything bad to say about them aside from the occasional aiptasia nipping.