Check out this page:
http
/members.ozemail.com.au/~thebobo/goby.htm
It's written by a very experience mudskipper collector and keeper. Richard knows his stuff and is has produced a helpful but short care sheet if you want to get a handle on the basics:
http
/members.ozemail.com.au/~thebobo/care.htm
But, as others have said, these are brackish water fish. Exact salinity actually doesn't matter, anything from 1.005 to 1.018 will do, and if you can vary it with each water change, so much the better. The traded
mudskippers are astonishingly hardy and need only basic filtration. The important things are these:
1. They need humidity, so think vivarium with a tight fitting lid, rather than fish tank.
2. They need much more land than water. Basically enough water to wet their bodies.
3. They grow big. Expect fish around 15 cm when mature, and potentially more.
So you need to work around the idea of a tank at least 100 cm long, mostly filled with rocks and sand, and then fitted with a glass lid to keep the humidity high. Not difficult, but certainly different to the usual tank.
Forget about adding tankmates. Unless you have a really large aquarium, adding things like archerfish or scats is impractical. Even adding small crabs tends to be a hassle; they either get eaten (if too small) or molest the mudskippers (if too big). Snails, like those neat
Nerites around these days, would work fine though.
Cheers,
Neale