I picked up a pistol shrimp along with some rock flower anemones and a mini carpet over the weekend. The pistol shrimp went right to work digging its burrows. by the end of the day my purple fire fish paired up with it and is now sharing the burrows with him. I know the fire fish is a goby, but I haven't heard of them pairing up before. It was very shy and would only come out to eat. Now it's always coming out of the hole in the front of the tank with the shrimp right behind it. Its pretty cool. I will try to get a pic and post it.