Pairing up gobies

[J2T]

Tried searching but didn't have any luck finding an answer. I have two different pistol/goby pairs in my 75g and would like to possibly get a second goby to pair up with one of the others. Anyone have experience or can lead me in the best direction on going about this? From what I gather it isn't possible to sex gobies before hand but what would be the best method? Should I be prepared for any aggression?

I have a Randall's paired with a tiger pistol and a YWG paired with a candy cane. Each of these pairs are setup on opposite sides of my 75g. Thanks for any help

 

[LobsterOfJustice]

I worked with watchman gobies for 2 years establishing pairs and trying to rear offspring. Basically, it's a crapshoot. You put them together, sometimes they get along, sometimes they want to kill each other.

I can tell you that even breeding pairs don't "hang out" together or live in the same burrow all the time, and in the wild they are often found one fish per burrow.