If you can make it to the Aquadome in ATX they have been stocking a lot of mini fishes as of late. I'm a huge fan of red cap gobies, yasha gobies, tiger or AKA clown goby (they are really neat since they hang upside down inside caves waiting to pounce.) Oh hey wait that's the list we have in our 7g, 2x red cap, tiger goby, yellow watchman goby, cool little red with blue stripe (like a catalina but not), fire shrimp and finally a tiger pistol shrimp. They all have their little places and get along very well. Usually you can only find one fish at a time and the pistol is always tunneling and shoving sand out it's hole. He was bought to pair with the tiger goby but instead became close friends with the yellow watchman. When food hits the water everything comes out including the tiger pistol shrimp.