Shrimp will eat anything they can. Like crayfish and lobsters, they are opportunistic feeders so I suspect that a smaller fish might just become lunch if it ventured too close. I have one shrimp like Bruckm and 4 others of similar size but different species in my tank. So far they haven't injured any of my fish but let them dent one of my loaches and they become Polypterus food....in bits and pieces, if necessary!