My rocks have turned black... but indestructible.

[Jay Hanig]

I don't think the stain is just black algae. It stood up to enough algacide that the water covering the rocks looks like drinking water. It stood up to full strength power washing. It stood up to bleach.

So now I have a test rock that has sat in 3 gallons of water and one cup of HCl for almost 24 hours and zero apparent results. I added another cup of HCl a few minutes ago. If that has any positive effect, I will clean 2-3 rocks a day until the effect is pleasing. I don't mind the occasional dark rock; I just don't want the entire bottom lined with them.

BTW, the rocks will be soaked in progressive rinses before they return to the ponds.

 

[Meyer Jordan]

It may be cheaper in the long run just to purchase new rock.

 

[morewater]

It may be cheaper in the long run just to purchase new rock.

That's a lot of work for just rocks. Farmers stack them in piles at the edges of their fields. Rocks are everywhere. They're very slow and easy to catch.

 

[Meyer Jordan]

That's a lot of work for just rocks. Farmers stack them in piles at the edges of their fields. Rocks are everywhere. They're very slow and easy to catch.

Not is my neck of the woods. They are an extinct specie!!

 

[tbendl]

Not is my neck of the woods. They are an extinct specie!!

He's right, you can find the bones of them scattered all over the beach in super teeny tiny pieces....

 

[pecan]

Rocks are everywhere. They're very slow and easy to catch.

This made me laugh.

I have no advice to the topic at hand though, so good luck.

 

[barryian]

The muriatic concentration should be one part muriatic acid to 3 parts water. NO BLEACH !!!
The one cup you added to all that water would have no effect as you saw ... and then, there's always the rock replacement ...

 

[TAHOE]

Bleach + ammonia will kill you. I don't know what bleach + acid would do.

Muriatic acid is another name for Hydrochloric acid,
Ammonia is a base
Bleach is a base,
you usually can't mix a base and an acid without getting a nice poisonous gas left off.

Not sure you will get rocks clean short of sandblasting them or letting them sit in a very concentrated solution of the acid. You can use it to clean concrete and whiten that up, but concrete is porous unlike most river rock or the like.
I have rocks that were in my pond that were covered in algae, they all have a dark green look now, but I like it.