I'd dump the carbon altogether if I were you. It won't pull salt out, but it pretty much pulls everything else out, both good and bad. Lots of discussion about it's effect on large cichlids such as Oscars and possible links to HITH.
It's impact on trace elements is a big topic of discussion around the internet and it's effectiveness is generally short-lived. Pretty expensive way to accomplish what weekly water changes will do better. Just my opinion here of course