Rhinogobius wui hails from Hong Kong, it is normally a brackish water goby but has been kept by many people in salt densities of completely fresh all the way to almost marine.
They are not outstandingly colored but their comical behavior makes them a winner in my fishroom. Wui's obtain a maximum length of around 2 inches (5cm) and can live comfortably in a tank as small as 5 gallon.
They are very hardy and are happy in temperatures between 68F and 80F (20-26.5C). One male will take the dominant role and any other males in the tank will assume female coloration. There are plenty of small skimishes, and they like to sneak up on their tankmates and nip them on the tail, but there is no damage done, it is mostly just for show.
Females are a mottled brown or tan close to the same coloration as non-spawning males. But the dominant male will be wearing his spawning and/or excited dress most of the time.
If you really want a show just place a small mirror up against the side of the tank and the male will spend an afternoon trying to outdo the fish in the mirror. This trick is one of my favorites and it also works wonderfully well for Bettas, Killifish and some Cichlids also.
Wui's spawn in typical goby fashion, they lay eggs in a small cave and the male guards the eggs.
Here are some more pictures of my wuis, they are excellent photography subjects and seem to enjoy the camera.
A male is checking out his own reflection in a mirror
The same male, now "mad" at his reflection. This is a typical pose for the dominant male, it reminds me of a wolf howling. He's showing that he is the baddest fish in town and not to be trifled with.