Another excellent reef fish is a fire goby, or fire fish and they come in three varieties, red, purple, and the rare deepwater Helfrichi.  All three types are hardy reef inhabitants and should be kept in groups of two or more, you can mix species if you add them to the tank at the same time. Maximum size is 3.5” so they work well in a nano tank. They are carnivorous and should be fed brine shrimp or other finely chopped seafood.  The red variety is commonly stocked at our store for ten dollars or less.