Elactinus oceanops
Also known as Neon Goby.
The Neon Blue Goby is a peaceful and easy-to-care-for fish. Its striking black and blue coloration adds a beautiful touch to any tank. As a carnivore, it can be fed a variety of foods and is equally suitable for a reef environment. With a maximum size of 2", it's a great addition to tanks as small as 10 gallons.