Can algae even behave this way?

[Swimgirl]

Hi.
I have some strange black looking spots on the bottom of my pool that did not vacuum up. I was able to scrape a few off with my fingernail, and I could see that the little bit around and under my fingernail was actually dark green, not black. But my pool water itself is very clear, even sparkling. If this is algae, it's just in little colonies on the bottom and none floating in the water. I don't seem to have had any strange amount of chlorine loss.
I haven't done a full set of readings yet to see if I have any CC.
TC=5
Ph=7.6
CYA = 55 (about 1 wk ago)

 

[jblizzle]

Sounds like you got black algae. See: Pool School - Black Algae

The CC level will not necessarily tell you anything. You can have algae with no CC.

 

[Swimgirl]

Sounds like you got black algae. See: Pool School - Black Algae

The CC level will not necessarily tell you anything. You can have algae with no CC.

Yuck. That's what I was afraid of. I just took a DPD chlorine test, and have no CC, but if I can have algae anyway, no good.
I have my CYA on the high side by design; I see you're in Tucson, you know how the sun burns the chlorine! But it also means that fighting algae is more difficult. The few times I've had algae I "cheated" a little and used polyquat, but I haven't had this type before.

 

[Swimgirl]

I looked at the pool school stuff on black algae. Yep, since it's green when I scrape it up, it does sound like black algae. However, I do have an above ground pool so it's vinyl, and pool school says it's usually on plaster pools. Guess I'm special. But since I can't use a stainless steel brush with it, what's the best way to remove from an above ground pool???

 

[JamesW]

Slam and brushing.

 

[chem geek]

Your bottom circulation is probably poor so after you remove this algae via frequent brushing to get the heads off and expose the roots to elevated chlorine, you can see what you can do to get better water flow in the area where the algae was growing.

 

[Swimgirl]

Your bottom circulation is probably poor so after you remove this algae via frequent brushing to get the heads off and expose the roots to elevated chlorine, you can see what you can do to get better water flow in the area where the algae was growing.

What kind of brush works to get the heads off, but is safe for vinyl? Pool school's instructions are for a plaster pool. My brush doesn't do anything but slide over the heads; I have to use the plastic on the end of the brush, a fingernail, etc, to scrape them off.

 

[JamesW]

Just use a plastic bristle brush. Lots of brushing and maintaining shock level.

 

[kimkats]

I would see about getting some brushes you can strap to your feet and see if they help. Otherwise I see LOTS of diving down to scrap the dots with your poor fingers.

Kim