I've had Cleaner shrimps in my tank and they always get eaten, no matter how much I stuff the CA Ray, Bamboo, Coral Cat Sharks or Groupers I have in the tank with food. Tried dropping in replacement cleaner shrimp and seems they barely make to to the bottom before being slurped up. I gave up. But I have several XXL hermits and small hermits in the tank which are left alone till they try to swap shells. The grouper watch them as they swap and can swoop in and snatch them up.