I know you can get a watchman goby and a pistol shrimp as a pair but I have also heard that each species of shrimp goby has a certain species of pistol shrimp that pairs with it. If this is true, what are the common pairings? Also is the pairing something I can do myself?- meaning can I separately buy a goby and the corresponding shrimp and have them pair? If someone could clear this all up for me that would be great!! Thanks