The little marks of algie took two scouwering pads to clear. I used a strong cleaner which had to be diluted with water. On the rest of the GRP fibreglass I used normal boat soap. It looks better as you can see from the before and after shots. It wasn't too bad but without watching for these things a nightmare too easily arrives.
Aaron Dia Pemberton. RYA qualified skipper. Trawler yacht captain of T&Eadapt