Putting the shrimp directly on the rock is a good idea. The first one made it to the rockwork, but the second one just was swimming against the glass. You should have seen the evil eye the pseudochromis had just before it attached the shrimp
<--- yes, like this.
I'm sure the one in the rockwork will be eaten as well, since it was smaller.
Well, next time I'm getting a big @ss peppermint shrimp that can fight off the fishies.