Why slime on push-on shower hose but not on fittings?

After several months of usage, the hose of a push-on shower spray (
http://www.diynot.com/img/ht/plp004.jpg ) can get black slime and mold(mould) on the inside.
However the same push-on shower device will NOT get any slime on the rubber-like cups which push onto the taps. Nor will it get any slime on the plastic shower head.
Why does only the main hose get the slime?
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Maybe the nonslimy parts have a microbicide/antibacterial agent compounded in them?
John
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David Peters wrote:

Slime is produced by a slime bacteria. Many metals, such as silver, zinc and copper are quite good bacteriacides. So if the fitting has any of these metals in it, slime bacteria will have difficulty growing on it.
Marshall
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David Peters wrote:

The hose is yummy to the organisms and has a nice surface topography for their persistence. Occasionaly clean the hose with a quat detergent or soak in diluted chorine laundry bleach. Use gloves either way.
--
Uncle Al
http://www.mazepath.com/uncleal /
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