Ladydi,
Sorry to hear about your peppers.
I have had 2 serpent stars for over a year who stay on the bottom and have been very good in not bothering my white-banded cleaner shrimp and my one peppermint shrimp. I have not seen the shrimp hang out on the bottom, but instead stay up in the rock structure. I have a clarki clown who grabs mysis shrimp or any other larger pieces that he can't consume, and dump it in front of the serpent star as though he was feeding an anemone. I thought it odd, but he must know the star is hungry. I love my stars, and up til now, I can't give them a bad rap.
Perhaps your shrimp weakened during the acclimation and succumbed to being dead meat for the stars? You know that shrimp need a long, slow acclimation to new water and sudden changes in pH, temperature or salinity can be fatal?I hardly ever see my peppermint as he is ALWAYS hiding out in the live rock. I target feed the shrimp with brine shrimp from a turkey baster. Have you tried the white-banded cleaner shrimp. You can get them fairly large and seem to be quite hardy. I guess you wanted the peppers to kill aiptasia?