There's been a lot of discussion about the yellow watchman goby pairing with a pistol shrimp and our guys took to each other right away. Here's a little video of them: https://drive.google.com/file/d/0B4EuliVkuZpKRGV1aUhOenh4MTA/view?usp=sharing
The two pistols I've had were both added later than the goby. The first one I got was back when I had my original 10 gal tank. I had the YWG in the tank as my first fish, a couple months later I added the pistol shrimp and the pistol was clicking nonstop as it swam in to a hiding spot, the YWG came out and swam all over the tank frantically until he found the pistol and immediately buddied up with him.Very cool. Did you introduce them at the same time? I've had a YWG for a few years and want to try a pistol.