The black-ray goby (Stonogobiops nematodes) is also called the black-ray prawn goby, high-fin prawn goby, or black-ray shrimp goby. They belong to the family Gobiidae.
The black-ray goby is a small, beautiful, marine fish that only attains a maximum size of about 2 inches (5 cm) in length.
They are excellent fish for reef tanks and are generally peaceful fish. You should provide them with plenty of live rock to graze on as well as for hiding places. Their tank should have a sandy substrate for them to form burrows in. They often bury themselves in the sandy substrate if frightened.
Black-ray gobies are bottom-dwelling fish. In general it is best not to overcrowd the bottom of your tank with too many bottom dwellers as they will have to compete for food and hiding spots.
Although generally peaceful fish, you should only keep a male-female pair in your tank. If you attempt to keep two male black-ray gobies they will fight.
They usually form monogamous pairs. In their natural habitat they usually live in small burrows in male-female pairs. You should keep a mated pair of black-ray gobies if possible, as solitary specimans aren't going to be happy.
In addition, in their natural environment they form a close relationship with the pistol shrimp (Alpheus randalli). Because I believe that aquarists should attempt to mimic the natural environment of fish kept in captivity as closely as possible, you also need to keep this shrimp in your tank with your black-ray goby pair. The pistol shrimp lives in the same burrow with the male-female goby pair and they help to protect each other.
However, you must use caution when keeping the pistol shrimp with other shrimp species, such as the scarlet skunk cleaner shrimp (lysmata amboinensis), because pistol shrimp prey on these shrimp. See the You Tube video below for a demonstration of the pistol shrimp's predatory behavior toward other shrimp species.
Although pistol shrimp prey on some cleaner shrimp species they have a special relation with black-ray and other shrimp gobies. Your goby pair will not be truly happy without the pistol shrimp present.
Black-ray gobies are mostly carnivorous fish, but will sometimes eat algae. Feed them mysis shrimp, vitamin enriched brine shrimp, meaty frozen foods for saltwater fish, and finely chopped seafood. The pistol shrimp eats a similar diet.
These are interesting little reef fish, but they are often difficult to find for sale. However, obtaining them is worth it just to see their relationship with the pistol shrimp.