I have a Yellow Watchman in my Nano, I added a small Candy Cane Pistol after about 6 months and they still paired up, did take them 2 or 3 weeks though...Oddly enough I got a HUGE Tiger Pistol Shrimp recently on accident, the Goby switched over and paired with the bigger Tiger Pistol immediately, the tiny Pistol is still in there, just doesn't have a buddy anymore.