I heard Shannon Lush recommend Hy-Clor Longlife Algaecide with copper to brush on concrete and limestone for algae removal. She said 2 tablespoons of powder in a bucket of water.
I bought the liquid version.
Q1. Do you agree with her recommendation?
Q2. If so, how much liquid perbucket of water (~9 litres) should I use?
250240cookie-checkMould on liquid concrete
No. Use oven cleaner or any other source of caustic soda, and then mechanical action of some sort – hose, high pressure water cleaner. But you’ll never get it all off limestone. Limestone is a rich source of carbon that cyanobacteria love for the purposes of making biomass, and it’s not actually mould, so a biocide is a waste of time. You’ll notice that limestone walls are blackest on the parts that get the most sun, not the least, as is the case with mould.