I think there is a fairly good chance this is in fact an
Alpheus immaculatus. If you can get a top down shot, it will be easy to tell the difference between a few of the close relatives. Otherwise, you can just check closely to see if there are yellow or golden dots all over the shrimp. If not, it most certainly is an
Alpheus immaculatus. Here is a pretty good comparison shot:
The shrimp will not pair with any fish.