How to remove black stains from new Merbau deck?

[ineedadeck]

I have had a merbau deck laid this month but unfortunately has had some rather large black stains appear. Having googled I have tried to remove using baking soda but this has just made it worse and is now spread. Will tannin remover sort this? I’m worried about trying anything else  

[EricL]

Welcome to the Bunnings Workshop community @ineedadeck. It's great to have you join us, and thank you for sharing your question about removing a black stain on your deck. 

Congratulations on your new deck. Before I make any recommendations, would it be possible for you to post a photo of the deck and stains? This will give our members a better idea of what it looks like. We can then offer you suggestions on how to remedy it. However, with the description, you've given it might be mildew. This black staining often occurs on unstained decks where water has pooled for a while. We look forward to seeing the photos.

Eric