Whether a fish has scales or not is immaterial to its tolerance of salty water. Moray eels and sharks do not have scales, yet both live in the sea. Tetras and gouramis have scales, but are intolerant of brackish water. Catfish do not have scales, but there are at least two families of catfish that live in the sea (Ariidae and Plotosidae) and several families that have members that inhabit brackish water or the sea periodically (Aspredinidae and Bagridae, to name but two). There are even a few plecs that are natural inhabitants of slightly brackish water.
Salt-tolerance is to do with osmoregulation, specifically how the gills and kidneys are set up to conserve water and remove unwanted salt from the body. Some freshwater fish "recently" evolved from marine ancestors and still have some of the hardware in place for doing this. Livebearers and killifish, for example, often have a very high tolerance of salt. But most freshwater fish have been in freshwater habitats for tens if not hundreds of millions of years, and have little to no tolerance of salt because they have long since lost the hardware for dealing with salty water.
Anyway, on your list, the only fish with brackish water tolerance are the jewel cichlid, the ropefish, the and the needlefish (if
Xenentodon cancila). All three of these naturally occur in slightly brackish water, albeit not commonly. If your needlefish is one of the gar-like characins (check for an adipose fin between the dorsal and the tail fin) then it is intolerant of salt. By "parrot cichlids" you mean those ghastly hybrid things, right? Rather than Hoplarchus psittacus? If so, then being a hybrid it's impossible to know its tolerance of salt, but some of the Central American cichlids are quite salt tolerant. A few can even live and breed in sea water.
Rift Valley lake cichlids are intolerant of salt as a general rule (perhaps because they are specialised for certain water conditions). None of your catfish is salt-tolerant. Angelfish certainly do not like salt, being adapted to soft and acidic water.
So, no, you can't "just add salt" to this collection of fish, and sadly the goby should be taken back. Otherwise, get anoher aquarium, and keep some brackish water fish!
By the way, your collection of fish is a bit heterogenous. I for one would worry about mixing angelfish with jewel cichlids, and needlefish are a bit skittish, and hardly ideal animals for a tank containing aggressive cichlids.
Cheers,
Neale