Domestic discus would be fine with your tap water, as others may have suggested I also recommend removing the coral. The only "challenge" with discus is keeping the nitrates low and keeping them warm. They also don't appreciate fast moving fish or anything that might out-compete them for food, so a group of sterbai's and cardinals is the most I'd go for tankmates. I also suggest keeping the the scape as minimalistic as possible to reduce detritus, something like a "root structure" and a thin layer of sand.
Something like this would be ideal imo
Something like this would be ideal imo