Reefer74, I have tried that, and they will just come back ... seems like they live off acros at some life stage ...
I was worried to do an in tank treatment for years, and finally came around doing it about a month or so ago ( finally had enough of them after about 2 years) ... Absolutely nothing to worry about, even my shrimp is fine, acro crabs hung on for about 8 hours, but didn't make it .... Make sure to do a large water change after and put new GFO back inline.