KH is 16 in new saltwater mix?

[LeanneP]

I have heated and aerated my saltwater mixture for 48 hours and tested the KH and it is at 16. My tank is about 11.5. I am using instant ocean salt and my water is being filtered with a tap water filter that I got for aquariums from J & L. Is it likely the filter is increasing my KH? I rolled the salt bucket around before getting the salt out. Is there something I can use to decrease the KH before adding it to my tank so I don't have to do a new mix?

Leanne