Is this black algae?

[ValleySooner]

My newly constructed pool was filled on July 10th. Almost immediately (two days later) I saw noticed black spots on the plaster. I didn't think anything of it at the time, as the pool was new and water was just added. It may be my imagination, but it appears the number of black spots have increased. This has caused me to worry that I have black algae.

Here are a couple of pictures:

I included my shoe (mens 8) in the latter as a reference to the size of the mark.

Also, I'd humbly request referencing this thread:
http://www.troublefreepool.com/fc-goal-when-using-an-ozonator-t15617.html
for some recent history/details on my testing numbers.

Do you think I have black algae?

 

[reebok]

hmm it doesn't really look like it to me. the main thing that you should be able to tell is if it grows a thicker layer (biofilm) on top of itself. or you can try rubbing it with a trichlor puck for a few days and see if it dies. it looks like a pen exploded there to me.

 

[frustratedpoolmom]

Doesn't look like black algae to me. Looks like some kind of plaster defect or metal reaction maybe? Have you had the PB out to consult?

See Reebok's avatar....now that's Black Algae!

 

[ValleySooner]

hmm it doesn't really look like it to me. the main thing that you should be able to tell is if it grows a thicker layer (biofilm) on top of itself.

They're not slimy yet... so I don't think it has a top layer at all.

or you can try rubbing it with a trichlor puck for a few days and see if it dies. it looks like a pen exploded there to me.

Is that safe to do with fresh plaster? I'll give that a shot if it won't discolour the plaster.

Doesn't look like black algae to me. Looks like some kind of plaster defect or metal reaction maybe? Have you had the PB out to consult?

I'll be sure to ask him when he's out here next. My biggest worry was that a small problem would start to get larger... but luckily, as you noted, my pool doesn't look anything like reebok's avatar, thank goodness!

 

[reebok]

haha, actually that's thick, dark green algae kind of like you see in a lake. I didn't get black algae until my pool was redone in 12/07 (that picture was taken during the drain process of replastering). it grew on a rough spot at the sun deck where the tile on the steps is. if you don't want to wait to see if it grows a biofilm, you can brush it and it should disappear really easily in one brush. then it will come back in a couple days. so you're still waiting, but you're avoiding the trichlor puck (which I don't think would be a problem, but better safe than sorry) but if you find it isn't an easy brush off, I would call that more evidence it's not algae.

 

[duraleigh]

Black algae typically occurs in pools that have been neglected a very long time......two days is not enough.

 

[X-PertPool]

black algae looks more like black felt dots, when use brush them hard they float off into the water but don't really cloud like other algae, and sometimes they leave a black ring where they were affixed.