What's a good way to clean a patio?

[Stravaig]

Dunno if this is the right place to post but I didn't see anywhere better. It isn't a patio anyway. It's quite a large concrete-slabbed terrace outside of a sixth floor flat.

We have a bird bistro which attracts quite a lot of small birds, so naturally we're getting plenty of bird droppings. Plus there's now starting to be quite a growth of green stuff. Moss? My idea was to get a brush with very stiff bristles and probably some kind of chemical cleaner. Obviously I don't want to hurt our birdie customers at the bistro.

Any ideas, please, what we should do without harming any of them?

Thanks in advance.

[Primrose]

probably a good stiff brush with lots of hot water with Fairy Liquid or some similar liquid soap. I suspect any stronger chemical cleaner could probably cause damage to the concrete?
Mould or moss is probably inevitable if the position is in shade for much of the day but whatever liquid you use might drain off and splash down on the windows of the occupants immediately below making you a tad unpopular, especially if the windows arn't cleaned regularly ?

[Stravaig]

Good advice, thanks, Primrose.

The design of the building means that those of us in the lofty heights don't have people below suffering from our actions (or inactions).

I think a stiff brush and a mild chemical, eg Fairy, will be the best place to start. If that doesn't work I guess we consult the landlord.