I read an old post on here that 'Peanutbutter' started.
Thought I'd resurrect it as I know there will be hundreds of you that will be continuing to have to same problem now, as I have done.
I've found a sealant that really works!! It doesn't have silicone in it and that's 'why' it doesn't go mouldy!
It's called CT1 and it's designed for wet areas, can even be applied 'whilst' wet!
Here is a link to a supplier I found on line: www.sealantsonline.co.uk/ProductGrp/CT1_Unique_All_in_One_Sealant_Adhesive
I have no affiliation with this product btw, just love it! Though it's a little pricey (£11 tube) it will actually save you time, effort and money in the long run!
Let me know after a few months, if you've tried it and tell me what you think!