On 06/11/2020 21:28, alan_m wrote:
On 06/11/2020 20:59, F wrote:
We've got a patio made up of light coloured concrete paving slabs with a
slightly rough texture. I've used a Karcher power washer to remove the
compost that the resident gardener has managed to tread into them but
there's a green stain (algae?) that's pretty resistant to removal.

Anyone got any suggestions on what might shift it?


Bac 50?

https://mistralni.co.uk/products/c10...um-chloride-ba

I've used it to remove algae on a transparent plastic roof. Sprayed on
and left for a week or two before washing again with clean water from a
hose.

Thanks. It sounds to need some fairly serious [protection when spraying
it. How plant-safe is it?

--
Frank