Over the years I have tried a few different ways to pair a goby and pistol shrimp. Some worked and some didn’t, but they all did eventually find each other.
If you add your pistol shrimp first it will immediately begin digging its way beneath a rock, firstly to escape any danger and secondly because that is what they do. If you then add a shrimp goby there is absolutely no guarantee that it will find the pistol shrimp straight off the bat. The first thing the goby is interested in is finding a hiding place to escape danger. Both of these guys are super into ‘stranger danger’.
By adding both at the same time there is the strong possibility that each will go their own way. As much as they what to be together, their number priority is to escape danger. I did try this in my most recent introduction and it looked good few a few minutes, then they split up.
My most successful pairing was introducing the goby first. The goby went into the tank a few weeks before the addition of the pistol shrimp. What this achieved was the goby was able to settle in one spot and barely moved from there. I then introduced the pistol shrimp down a pvc pipe directly to the goby. This was an instant pairing.