Black Algae or Not?

[Aflick]

My pool was completed in October and I have noticed these spots on the bottom for a couple of months. Is this black algae? It's hard to tell with the pebble finish and the water temperature is 62 so I have not gotten in to inspect closer. I have brushed multiple times with no luck.

Before starting to treat for Black Algae, I thought I would get other opinions on whether or this is black algae. These are the best pictures I could get (look for the black spots :

 

[Dirk]

Did you see that they actually appeared? Or could they have been there the whole time?

I have a small amount of glittery flakes in my new pebble (also done in October), that I didn't order or want. I figure they were in the mixing bin (whatever they use to mix the pebbles together to get the desired color mix), leftover from some previous job. Could those shapes be someone else's color chips?

On one occasion, I saw black stains that I also thought might be black algae. I thought it might have somehow survived from the old plaster, which was diagnosed with black algae, so I freaked. They wouldn't scrub off. Then a few days later they were gone. Something organic, stuck enough to resist a scrub, that eventually succumbed to chlorine doing its job.

Maybe give 'em another few days? Now that you have pic's, you can compare if they shrink or grow?

 

[Aflick]

There seem to more developing. I added the remainder of the bleach I had on hand to increase the chlorine level and will start treating it.

I hate that a new pool has this issue.

Did you see that they actually appeared? Or could they have been there the whole time?

I have a small amount of glittery flakes in my new pebble (also done in October), that I didn't order or want. I figure they were in the mixing bin (whatever they use to mix the pebbles together to get the desired color mix), leftover from some previous job. Could those shapes be someone else's color chips?

On one occasion, I saw black stains that I also thought might be black algae. I thought it might have somehow survived from the old plaster, which was diagnosed with black algae, so I freaked. They wouldn't scrub off. Then a few days later they were gone. Something organic, stuck enough to resist a scrub, that eventually succumbed to chlorine doing its job.

Maybe give 'em another few days? Now that you have pic's, you can compare if they shrink or grow?

 

[Dirk]

Stand by, I'm pinging someone for you...

 

[kimkats]

I hate it for you as well! One thing you can do is put a chlorine tablet in a sock and zip tie it to a stick or something you can reach one of the spots with. Rub one of the spots and see what happens.

IF one of them is on an area you can reach with your hands you can see if you can scrap some off with your fingernail. Wipe it on a white paper towel. Take a pic and show us. If it is black algae it should look dark green on the towel.

 

[Aflick]

Unfortunately I can't reach the bottom without getting in and it is too cold (for me) to get in. Hopefully it will warm up enough over the next few weeks to get in.

I hate it for you as well! One thing you can do is put a chlorine tablet in a sock and zip tie it to a stick or something you can reach one of the spots with. Rub one of the spots and see what happens.

IF one of them is on an area you can reach with your hands you can see if you can scrap some off with your fingernail. Wipe it on a white paper towel. Take a pic and show us. If it is black algae it should look dark green on the towel.

 

[kimkats]

I hate that you have to treat this new plaster (not a yr old yet) for black algae but you do what you got to do!

 

[bproosow]

What are your chemical levels at?

 

[Aflick]

Here is a close up photo. Here are the chemical levels:

FC - 16 (I kept it at 20+ for 5 days and it is coming back down)
PH - 7.4
TA - 90
CH - 275
CYA - 40

 

[Razorhog]

Looks brown like rust to me. Have you tried rubbing a Vitamin C tablet on the stains?

 

[Aflick]

Looks brown like rust to me. Have you tried rubbing a Vitamin C tablet on the stains?

That is what I was thinking as well. I didn't realize that a vitamin C tablet would help. I'll try to get my hands on one. Thanks!

 

[Razorhog]

That is what I was thinking as well. I didn't realize that a vitamin C tablet would help. I'll try to get my hands on one. Thanks!

If it is iron, Vitamin C will take it off like magic. Then you’ll need to assess the cause of the metals and treat accordingly.

 

[Dirk]

Oh, geez, if it's rust, I hope it's not something embedded in the plaster. My plasterers made a big stink about me working on the roof while they were shooting plaster. They've had roofers' nails fly off a roof into wet plaster, only to be discovered after it cured, as rust stains emerged from underneath. Finger's crossed for ya!

Sorry to put a scare into you if it's needless, I mention this only as a troubleshooting possibility. Maybe mark somehow where the stains are (a square of tape around the stain) before you treat. If the Vit C determines it's rust, and it goes away for good, you're good. But if it comes back in the exact same spot, then you might have something buried that's rusting from the inside out...