Help with green rocks

[Soulphire]

Hello all! I have a pondless water feature that I built about 4 months ago. Everything is working great, but now my rocks have turned green.
What is the best product to use to get them back to their normal color? The rocks do not have algae on them, but I think they are actually stained?
No plant life or fish.

Please see photo for reference.

Thank you in advance.

 

[Lisak1]

That is indeed algae. I'm assuming no fish.- do you have plants in the feature? If not, you can use an algaecide or even a small amount of chlorine bleach (would not be my first choice however). You can also use hydrogen peroxide, either sprayed on the rocks or added to the water, which is a much safer route to go. But adding plants to the system would also help greatly!

 

[j.w]

@Soulphire
I like the hydrogen peroxide way as prolly much more safe for any critters that come for a drink.

 

[Soulphire]

Thank you very much! I'll go the Hydrogen Peroxide route since a lot of birds and deer drink from this.
Any special kind of hydrogen peroxide, or just the one I find in the first aid section of the grocery store?

Thanks!

 

[Lisak1]

Just plain old drug store variety. You'll have to experiment with amounts - but you can't really overdo it.

 

[Soulphire]

Awesome! Thank you so much!