Treat patio slabs etc BAC50 ,BA50
Benzalkonium Chloride Algaecide Bactericide & Fungicide clicky
strong stuff
very effective
How long is it effective for?
it's like wiping the slate clean ,kills all the algae ,germs ,mould spores
how long before they come back is down to environmental factors .
Like systemic herbicide /weedkiller ,It displays high degree of biodegradability,
like a new patio ,it should take quite a while before algae returns
the link (other sellers/websites available ) is for 5 litres ,if you dilute 1 to 8 , that's 45 litres (read the data sheet depending on application)
(don't mix that much unless you have a big carpark or road to treat
)
that £30 tub may last you 5 years or more
time is money ,patio washing may be a relaxing/enjoyable "pastime" to some
as is sitting in a comfy chair, ON the patio, drinking beer to others