Re: Moss
The old Jeyes fluid worked well on algae and moss but like a lot of things it was changed to comply with EU regs and it is not as good as it once was and yet still smells awful.
A lot of 'moss killers' also contain iron which can stain a nice patio. Some folks use a solution of Glyphosate but it is dangerous stuff to use with animals about.
It is ok to use a very dilute form of thin household bleach (Sodium Hypochlorite) but always add the bleach to the water not the other way round and keep plenty of clean water handy in case of mishaps.
Being bleach it can also damage any plants or grass so one has to be careful and it might take several applications to shift it and then has to be repeated every so often.
The simplest thing I have used for years is nothing more than clean sharp sand and a broom , oh and yes a great deal of hard work scrubbing it. It is worth the effort when you see the results and it lasts because you lift the tiny moss plants off the surface not drown them.
Good luck.