Are those the rusty looking stains from the iron content? They don't come off easy. Muriatic acid might help, but will leave a slightly different texture and color in the area it was used, and isn't always effective.

Well I didnt know that Tugb, as I have never used this product I have just looked on line at the packaging and it has a tiny warning that is so small I doubt anyone sees it!
STAINING - Do not walk on the lawn until the
product has been watered in, since moss killer
can cause stubborn brown stains on clothes,
paving slabs etc. Brush off immediately if
accidentally spilt.
This must be disappointing for you Foz,
Sorry the packaging does not say how to remove stains. Take some photos and send them to the company and see if they come up with a solution? I presume you have tried a patio cleaner?

Um, I don't think there's any way of removing it - there is advice not to get it on hard surfacing, or at least there used to be. I think its not so much staining as pitting or damage to the surface of the stone.

I have just had a look at a pack in the GC and the tiny warning (that I copied above) is still on there Bamboo. Whats in it that damages patios/stone?

Strong chemicals - fine on grass, usually its the mosskiller element which causes damage. Leave lemon juice on a paving slab and see the damage later - we eat them, but the juice is strong enough to dissolve limescale, and damage stonework.

Thanks Bamboo

I understand now. I answered the way I did because I am used to having troubles with the iron content in the fertilizers we use here. Often they react with concrete or high lime stones to leave permanent rusty brown, orange or yellow stains. Manganese sometimes leaves umber or purplish stains, too.

This turned out to be an interesting question. Its been helpful to me to hear about the chemicals and Iron staining/damaging stone/patios etc. Thank-you all from me. Sadly there seems no quick fix for Foz?

Try a good concrete rust remover should work a treat.