Black spot algae on rocks

[Karen0330]

Hi Everyone! I have a small backyard pond and struggle with (what I call) black spot algae on rocks. When I search it I can't find any pictures of it (and I don't have any) or any mention of it. Does anyone know what it is?
The spots look like mold spots and start small and grow. I think if I didn't scrub them off (which is difficult to do, I use a hard toothbrush and it often doesn't get it all off) I think they would end up covering the entire surface of the rocks. Only the part of the rock that is exposed to the sunlight grows the algae. Does anyone know what this is called?

 

[MitchM]

Welcome!
What part of the US are you in?
Google some images for "Black Brush Algae" and see if that's what the algae looks like.

 

[Karen0330]

Hi Mitch- I live in upstate NY. I looked at the BB algae. What I have is not hairy, it's more of a crust. I looked around on-line some more and am pretty sure it's black algae. The pond gets a lot of direct sunlight, so I'm going to find a way to give it some shade. I just need to figure out how to kill the algae. I have drained the pond and will work to get all of the debris out. It won't have fish in it for about a month, so I am willing to use something strong to kill the algae. Any ideas? There's not a lot of information on how to kill black algae in ponds!

 

[Meyer Jordan]

Could be fungus or slime mold. Got any photos?

 

[Smaug]

Don't sweat the small stuff in a pond. If you really have to go after it with a toothbrush it's not likely something you can win against. It's also not likely something that's indicative of a big problem either.

 

[sissy]

Most algae will die if you spray it with peroxide .Some algae is good because it helps clean the water ,especially when none of the plants are growing in the pond