Parksfan, I love your pictures!!

I'd love to do a patio like that but our back yard is very shaded by large trees that aren't ours. So dark it's difficult to grow grass (or even weeds) back there.
Our neighbors with wood or concrete patios & stepping stones often get green mossy stuff growing on them. Also homes throughout our neighborhood that have replaced the shingle type siding with vinyl siding have this problem. So many trees all over but we do love them.
Does power washing clean it off or would you have
to add some bleach to it? Would that ruin a decorative concrete like that? Just curious...
Honestly, we have a screened back porch that we hard use so I can't say it's "burning a hole in my pocket" as OP said. I think we've been putting it off partly because we don't want something that would end up being high maintenance but also that we don't spend a lot of time in our back yard.