Hi Brian and welcome to Simply. I would suggest doing a lot of reading here on the site about basic discus care. You will find that starting with a sterilized tank and a fishless cycle is generally recommended here. The problem starting with your cichlid filter sponge is it is a source of contamination with a new group of discus. While aragonite substrate and lace rock are ok for African cichlids we recommend a bare bottom or a lite layer of PFS for discus. As a begineer I would suggest starting bare bottom until you are comfortable with discus.
I would encourage thinking about a water change strategy as discus require lots of clean water.
Pat