On 07/11/2020 09:37, The Natural Philosopher 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?

Green goes with bleach and heavy power washing. Its the black ones that
are impossible to shift.

We have black too. Forgot to mention that.

--
Frank