I know what you mean...I figure they go mouldy because water gets in but can't get out. I try washing them out, but it never all gets out, does it? If you bleach them, the bleach might not all come back out and do you really want bleach with your kids toys? I suppose that means chuck 'em, doesn't it? unless you're happy with mouldy bath toys? Now you're making me feel bad that DS has mouldy bath toys