Hi, my pressure washer has broken. Most of my stones are clean but the
pressure is no longer high enough to get off all the algae.

I see there are liquid cleaners I can pour on but I imagine this does
horrible things to the insects living below (the stones are set on
supports).

Just on the offchance before I buy a new washer, is there an
environmentally friendly way to clean the stones without a washer?

Thanks a lot. Apologies if this is too off topic.

C.