I have them with cherries and in over a year I've only ever seen them catch one shrimp... I more often see the shrimp riding them around. The one shrimp they caught was likely sick and whole they're there my shrimp population has continued to expand just as quickly as before I added them. If you have a healthy shrimp population assassins likely aren't going to make an impact even of they do happen occasionally across an unlucky shrimp when they are hunting.nice. i really like those but i have red cherry shrimp and they are known for attacking shrimps.