Shower Mould: Black vs Pink — What Each One Means

Not all shower discolouration is mould, and treating everything as if it is wastes time and cleaning product.

The dark, blotchy staining in silicone and grout is genuine mould. It grows on organic residue on wet surfaces and it's a health issue when severe. Full removal of the affected silicone is the reliable fix; a deep clean is the temporary one.

The pink or orange staining that appears in shower bases, around drains and in low corners is usually Serratia marcescens — a bacterium, not a mould. It feeds on soap and shampoo residue and thrives in damp, low-flow areas. Regular cleaning is usually enough to keep it in check; it's more a cleaning issue than a repair issue.

Green tint on grout is often algae, driven by consistent moisture and low light. Same category as the pink — cleaning issue, not repair issue.

The category that always needs proper attention is black mould embedded in silicone. Surface cleaning won't reach the growth in and behind the bead. Full silicone replacement is the fix.