Fluxaf Graffiti Kleaner the most effective Algae and Moss killer ever spray,brush,or roller on, leave and within 24 hours the results are amazing only leave on none painted surfaces,on painted surfaces wash down within 3-4 mins with water.if you have not tried this product you need to it is incredible.
This looks like good stuff but haven’t tryed it myself has anyone else
We have a job on patio to do you could try soda crystals leave down for a few days.
Have you got more detail on this approach? Photos would help if you are able.
We have two jobs coming up, with problem, will only be to pleased to add photos.