Pistol shrimps are capable and will kill and eat a symbiotic or potential symbiotic partner goby. Unless you purchased the two already as a pair, there is no guarantee that the two will pair-up.
There are prerequisites to pairing pistols and gobies. As Robert eluded to, pairing species that match well and are known to pair. Matching size between the symbionts is important. Smaller species shrimp with smaller species goby and vice versa.
The goby's appearance is also key. Here is a quote from an article written by Professor Ellen Thaler,
Coral magazine, Dec. '07/Jan. '08, Vol. 4, Num. 6; page 35:
Quote:
| ...The fish (goby) should not appear emaciated. In particular, the shape of the stomach must be convex (bulging to the outside) not concave (curving to the inside). Emaciated fish are rarely active, and will thus not react naturally toward pistol shrimp-which, in turn, makes the shrimp see them not as a partner, but as prey. |
Therefore, it's important to ensure that the goby is healthy and well fed before attempting to marry the two.