Since introducing Harlequin Shrimp couple of months ago, my asterina population has dropped to almost nothing. I used to pull 20/30 off glass every day or so. Now I rarely, if ever, see them.
Small nuisance snail that used to cover glass by the hundreds at night, have almost disappeared since arrival of sixline.
Rock that only a few days ago was thickly covered by little brown polyps (hydroids ?) - is now half bare. Added a dozen hermit crabs last week, and they seem to be mowing them down.
Thankfully (and hopefully) my "pest" plagues are getting under control with little additional effort from me.
("insha allah" - "God Willing")