Yellow Clown Goby (Gobiodon okinawae)
The yellow clown goby (Gobiodon okinawae) is a small colorful little goby from the family Gobiidae that only reaches about 1.5 inches (4 cm) in length. It is often simply referred to as "yellow goby."
Yellow clown gobies are excellent fish for reef tanks. In fact, they'll do best in a reef tank with lots of coral. They spend a good portion of their time resting in and on branching corals, such as Acropora species coral.
In their natural environment they often congregate in groups or pairs, however, in a small aquarium they will sometimes fight other members of their own species. Because of this, a lot of people advocate keeping only one yellow clown goby per tank. However, I think your goby will much happier with some company. What you should do is provide them with a spacious aquarium with a lot of branching coral and live rock to hide in. If everyone has plenty of room and plenty of hiding and resting spots in the aquarium then they will be more peaceful toward one another.
It is best if you can obtain a mated pair of yellow clown gobies. If a mated pair is unavailable, just make sure that your aquarium is large enough so that each goby can have its own territory and make sure you add them all at the same time.
In fact, if you provide them with enough space and coral in their tank they will often spawn in captivity, laying their eggs among the coral branches.
Aside from sometimes fighting with members of their own species, yellow clown gobies are peaceful fish. Also, don't keep them with aggressive or predatory fish. These gobies produce a toxic body mucous that repels most predators, but some predatory species may still attempt to eat or bully them.
Yellow clown gobies are carnivorous fish. You should provide plenty of well-established live rock for them to graze on as well as feedings of meaty aquarium foods for marine fish (e.g., vitamin-enriched brine shrimp, mysis shrimp, frozen aquarium fare for carnivores, and finely chopped up seafood.
Yellow clown gobies can be purchased for about $8 each.