Technically they're freshwater fish. But they inhabit artesian pools of water in desert regions where evaporation makes the water exceptionally hard and at times saline. To deal with flash floods they are also able to adjust to rapid changes in water chemistry, salinity, and temperature. So while they aren't estuarine fishes, they are much more like estuarine fishes than ordinary freshwater fishes. In home aquaria, they do very well in hard alkaline water with a small amount of salt added, around SG 1.003-1.005, but they can be acclimated to fully marine conditions or higher (according to Fishbase to around twice normal seawater salinity!).
These are exceptionally good aquarium fish. They are easy to keep and feed, and unusually for gobies easy to breed. The fry are not numerous but very large and take brine shrimp nauplii and powdered flake straight away. The only downside is they are almost annual fish, living at most for a two years. So if you get some, they're best kept in a single species aquarium so you can set up a colony. One other thing: they are partially herbivorous, so including algae in the diet is essential. There's quite a bit about them in the goby and Australian fish chapters of my book.
Cheers, Neale
