On Friday, July 29, 2016 at 3:30:06 AM UTC-5, Colin Roney wrote:
My plan is to remove patches of algae embedded in the GRP surface before
painting. So far, i`ve rubbed/cleaned down the surface as much as I can
using wire brush and glasspaper. Any ideas on the most effective product
to use please?

West Marine sells a mildew/algae and stain remover that works.