saralove999 wrote:
(snip)
I think I
might need some sort of high power water jet but I dont know if that
will destroy the decking. Please help!

I use my power washer on everything (to which I get totally obsessed
with - once I start I won't stop even if my face is frekled with mud
and my neighbours start standing on their front steps, arms folded with
a frowing face on. It's such a rewarding activity ;o). I use it on my
wooden benches and tables, decking, flags, concrete, stone, granite
etc. and even go around my ivy on the walls. Depending on your position
(far or away) from the items you want to clean, I've found you can
pretty much be 'gentle' (and can even make pretty paterns if you're
creative).

My advice, wear goggles and wellies. You're going to get soaked (which
is also very much part of the fun). Don't use chemicals. There's no
need. You'll only damage your environment because the algea/moss will
return next winter anyway.