Many thanks for that. We've now tried the following: Algae/moss killer (Patio Magic), Pathclear, Concentrated bleach, Rock salt, Mould and mildew killer with bleach, Dithane (fungicide), and Roundup. All of these were at double strength. NONE have killed it - you might like to mention that to your local guys.
Of the above, concentrated bleach was the best after covering it very thickly but it hasn't killed it. It definitely doesn't like being covered in a layer of rock salt but, again, didn't kill it. If we can't kill it, then spreading a layer of rock salt would be our best guess to try and, at least, reduce it.
Quick update. I've found reference to this on RHS My Garden forum. It's under "Gardening, Pests and Diseases, Seaweed like sludge in lawn". It appears to be called Blue Green Algae Nostoc Commune. They don't say how to kill it so will post that question on their site.
I have the same algae shown in your photagraph spreading over an area of limestone hardstanding, like you say it is worse after rain going slimey and green, and dries to resemble sea weed, I have tried most weed killers and moss sprays, bleach and now have resorted to removing and trying to bag it up to burn, but the task is daunting.
I am going to Bridgmeer Garden Centre Nantwich to see if there is someone who can give me an idea of how to destroy it.
I have the same algae growing in different places around my house. In gravel, on stone and in soil. I have also tried everything to get rid of it. The only way I can keep it under control is to remove it with a spade. But it always comes back. Thanks for your help in identifying what it is. I have been trying to find that out for the past year. Would be grateful for any new advice you may have on how to get rid of it all together. Thanks again
I have the same stuff on some mossy staddle stones and yesterday discovered it all across MIL's patio. Her algae has some very large pieces and also some small blackish bubbles. It is lethal to walk on and has covered her patio very quickly.
Just as a thought - two weeks ago we sprayed her patio with Roundup to get rid of grasses and other weeds in the cracks. I suppose Roundup hasn't got something in it which has caused this?
Has anyone any ideas on eradicating this horrible stuff?
Many thanks for that. Could I ask for an update perhaps in, say, one month. That would be brilliant.
Is there any update on this? We also have it spreading across the drive and we are about to try a flamethrower on it to try and burn it off!
was so pleased to find this identified as am despairing about it, but will now try the MMC-Pro mentioned
We have same thing going on the garden paths. We just found the stuff this spring . I want to kill it now !