I've been using soda crystals for various things around the house including stretching our washing powder, cleaning drains, removing grease and general cleaning for a long time and now I have another use: removing moss from paths, balconies, patios and verandas in an affordable and environmentally friendly way.
The photo shows what our balcony looks like a week after a single application and a bit or rain. Note the neighbour's balcony at the top of the photo. That's what ours used to look like.
When applying the soda crystals, I tested two methods: liberally sprinkle the soda crystals onto the wet balcony and create a strong solution and sprinkle using a watering can. Both proved to be very effective with the dry sprinkling onto the wet balcony probably being ever so slightly more effective on the first application as there would have been a higher concentration in spots than with the solution.
As you can see, things aren't 100% moss free yet, so I'll be applying a few more times, but I don't mind... soda crystals cost about £1 a kg which is waaaaay cheaper than the commercial chemical moss removers.