I have a 50gal tank. I would like pearl gouramis, columbian shark cats, and a bristle and peppermint plec. As the shark gets older I heard they need salt, if so can the other fish live in brackish water?
The gouramis can cope with tiny amounts of salt in the water, but keeping them in brackish water will slowly kill them. As kelly mentioned, b'nose and peppermint plecs have can't handle any salt in the water.
You'll need to buy a new tank for that shark if you want to keep him ot get rid of the other fish