I've used liquid grapefruit seed extract in water sprayed on bathroom mold to kill it, and it worked well.  Apparently citrus fruits have in their seeds natural compounds that inhibit mold as a way of protecting the seed.  There's also a concentrated powder form that would probably be good to use for scrubbing.

goes back to basic care and feeding of bathroooms, you have to control moisture to prevent mold spores from growing i.e. open window, fan, heat lamp, worst case wipe down shower tub area after use with bath towel

I'm an eco-friendly housecleaner and also have some sensitivity to mold and this topic is definately a challenge.  I offer a few tips:  I've noticed that 'new' mold is somewhat orange and can be cleaned.  Once it's black it won't come off many surfaces, as Umbra found.  Clean it before it turns black.  Even bleach, the nasty stuff, won't work on black grout, so don't even bother.

While I admit to not practicing this in my own household, (I know I could never get my housemates to do it), regularly squeegee-ing of bathtub/shower enclosures will help A LOT.  And it doesn't actually take as long as you might think.

Which leads me to an echo of above comment:  Keep damp areas dry.  The  bathroom in my house has no fan.  I've managed to get my housemates to regularly leave the bathroom door open after showering in the winter, or to open the window wide during summer.

And lastly a word on fans in the bathrooms.  If I could, I'd install a fan, even though the thought of having yet one more electrical machine in my house makes me want to faint.  Nevertheless, if or when I do install one it will either be on a timer, or will shut off automatically when humidity reaches a certain level.  It will also not be attached to a light fixture.  In most houses I clean there is an exhaust fan but you have to shut it off manually.  So if you take a shower in the morning, turn on the fan, and leave to go off to work, it's on all day, gobbling up more non-renewable resources.

Personally, I hope to someday escape civilization and live in a cave where I'll never have to shower again anyway!  Hmm, I bet there's mold in caves....

Be advised that the antiseptic property of grapefruit seed extract (GSE) is not from natural compounds. Not all GSE are made the same way. The grapefruit seed extracts that use a certain extracting chemical create a synthetic chemical, benzethonium chloride, which is the compound that has those properties. GSE extracts that do not contain this compound do not work as antiseptics. So, don't be fooled. Most GSE contains this synthetic chemical and so is not "natural".

Whenever I've used cosmetics with benzethonium chloride, I've experienced scarring of the skin. It was recently discovered that sodium benzoate and/or potassium benzoate mixed with ascorbic acid in sodas and fruit drinks make benzene which is linked to leukemia. There is no way I'd spray grapefruit seed extract all over my shower or use GSE in any manner.

Also, some people add GSE drops to water and drink it. According to the entry in Wikipedia on benzethonium chloride, taking it orally could cause neuromuscular transmission failure and should not be done.

Here are the titles of the journal articles that discuss GSE and benzethonium chloride in case you want to look them up.

> Pharmazie 1999 Jun;54(6):452-6   (ISSN: 0031-7144)
> von Woedtke T; Schluter B; Pflegel P; Lindequist U; Julich WD
> Institute of Pharmacy, Ernst Moritz Arndt University, Greifswald, Germany.

> J Agric Food Chem 2001 Jul;49(7):3316-20    (ISSN: 0021-8561)
> Takeoka G; Dao L; Wong RY; Lundin R; Mahoney N
> Western Regional Research Center, Agricultural Research Service,
> U.S. Department of Agriculture, 800 Buchanan Street, Albany, California 94710.