I do - een virtually neat esp with moss you can kill the top layer but underneath is still alive you end up with a horrid patchwork of moss/cleaned areas plus all the dead stuff will now roll into the gutter over the next few weeks
I much prefer to clean off moss leaving a clean roof from the time we leave site
biocide is great for algae and lichen covered roofs
I look at it this way - people see to treating the roof - the biocide doesn't work that well - customer tells people you treated the roof - your name is mud because people see the result is bad
I ised to get this when we either cleaned front only or uppers only - neighbours would ring and tell us the guys did a rubbish job snd didn't clean x,y,or z - now we only clean full properties
Darran