Thanks for your advice, it's a rental so no tearing out walls. Health wise I know it's harmless but it's wrecked a $100 shower massage and I go through a new shower curtain every month. It's bad. Would a simple in-line shower filter help at all with curbing the black slime? https://www.amazon.com/Culligan-ISH-200C-INLINE-SHOWERHEAD-FILTER/dp/B003RWSNBG