A little info,
http://aqualandpetsplus.com/Oddball, Butterfly Goby or Wasp Fishl.htm
and a cut+paste,
) Butterfly-goby waspfish (Neovespicula depressifrons)
Warning! This fish is venomous, and can deliver a vert nasty sting through the spines in its dorsal and pectoral fins. Avoid handling this fish, and never touch it with your hands. While the sting is not known to be fatal, as with any venomous fish, if you are stung, you should seek medical attention at once. Children and people who react badly to animal stings (such as bee stings) probably should not keep this fish.
Neovespicula depressifrons is a small, grouper-like predator that can easily be mistaken for a bullrout at first glance. Like the bullrout, it is predatory, but given that it only grows to around 10 cm in length, can be easily raised on small invertebrates such as earthworms, Gammarus, and river shrimp. Small fish are also taken, but besides the ethics of feeding living fish to another fish, this approach is expensive and can introduce all sorts of parasites and diseases (especially when cheap feeder guppies are used).
Neovespicula depressifrons is sold under a variety of names, including butterfly goby, a name also used for the true goby Awaous flavus. It is not a goby at all, but a waspfish, a member of a small family of chiefly marine fish that are well known for being venomous. In terms of maintenance it is not demanding. In the wild it inhabits a variety of waters from completely freshwater through to fully marine conditions, but in captivity it can be expected to do well in brackish water with a specific gravity from 1.010 upwards. Unlike the bullrout, it is a day-active fish, and usually swims about at the front of the tank looking for food. Anyone seeing a tankful of these fish will be instantly struck by their cute behaviour and surprisingly attractive colouration, which varies depending on the decorations in the tank. The body is a mottled brown, but there is a light stripe running from the nose along the ridge of the back. The pectoral fins are huge, and used like paddles. The dorsal fin is tallest at the front, and when raised makes the fish look like it has a mohican hair-do.
That is from
http://homepage.mac.com/nmonks/aquaria/brackfaqpart4.html
Other sources say 1 tablespoon per 5 gallons to 1 teaspoon per gallon of aquarium salt will work, marine salt is apparently not required.