Alright so I just got over this same issue. Do amphipods eat zoas/palys, you bet your a** they do. Is it intentional vs accidental; I have no idea. My belief is my system became over populated with these critters and I feed my fish heavy and with no real predator to eat these pods, their numbers soared. I first introduced a mandarin. The issue here was some of these amphipods were quite large and the mandarin just couldn't swallow them. So, I added a leopard wrasse. The wrasse seemed more agile and got around the tank more quickly than the mandarin, but the pods are most active at night... While these two fish did knock back the population; I soon added a coral banded shrimp. This was a catch 22, the shrimp comes out at night and it's my belief this is was really did the pods in, but every coral banded I've had has been very aggressive. I would go wrasse/shrimp and leave the mandarin out of the equation. My pod population has since been decimated and I've been charged with the task of getting the mandarin to take frozen; while i have been successful... some call these fish the hummingbirds of the ocean, I call them the sloths of the ocean. They eat as slow as molasses, if I don't target feed the other fish will out compete it for food. Here's a link to my YouTube video on the pods tearing up my Sunny Ds.