Tiny Black Dots on Plaster Pool Surface

[JW11779]

Hi, new to TFP. Can anyone help with identifying the cause & treatment for these tiny black dots showing up on my plaster pool surface? Some background; just completed an ascorbic acid treatment to remove some mild metal stains using StainFree and MetalFree products with moderate to good result. In the following weeks these black dots started appearing (see pics). Thought it might be black algae so I used a steel brush and Leslie's Black Algaecide to no avail. The dots won't even scrape off. Also seeing some new imperfections in the pool surface with darker stains in the imperfection. My numbers as tested by my local Leslie's:
FAC 6
TAC 6
Salt 3000
CH 250
CYA 80
TA 80
pH 7.4
Pho 0

Thank you in advance.

 

[YippeeSkippy]

Welcome to TFP

You dealt with metal stains.....then you added an algaecide made out of Copper. So you put back in that which you worked so hard to remove.

Its hard to know what's going on....especially as your trusting a pool store to do your important tests. We advocate for owner testing because you need to know the state of your water more than just once a month and pool store testing is notoriously inaccurate.

The two test kits we endorse are the TF-100 (much preferred) and the Taylor K-2006C both available from tftestkits.net or poolsupplyworld.com .

Using these kits will provide us with accurate:
FC (up to 50ppm and provides an exact number, not the color matching block which only goes to 5ppm and is questionable since you're trying to match colors)
CC
pH
TA
CH
CYA

...and no one cares about phosphates if the pool is properly managed with chlorine, except for Leslie's who wants to sell you a potion to deal with it.

Did your pool have any black marks before the ascorbic acid treatment?

Go grab a single chlorine tab (I believe you can buy singles from Leslie's?) and set it down on some spots for a few minutes and see if that changes it any? Then if it doesn't , go get some cheap vitamin C tablets and stuff them in a sock and smash them up a bit. Then hold that sock on some stains and see if that alters it.

It the chlorine puck alters it- its organic. If the Vit C alters it, it suggests metals.

Please don't add any more potions to the pool. Let us know how that testing goes.

Maddie

 

[JW11779]

Thank you Maddie! Appreciate the info regarding the testing kits. Trying the chlorine puck now. Will advise. And, yup, I'm a dork. Told Leslie's I already have copper algaecide at home and since I just completed an ascorbic acid metal stain treatment, I didn't want to add any metals to the pool. They said to use the Black Algaecide. I didn't even read the ingredients until just now, yep, copper. I have some ascorbic acid (basically granulated vitamin C?) can I sprinkle some of that right on those little spots?

 

[kimkats]

JW, Yes you can use the ascorbic acid as it is the same as Vit. C. Most people do not have it hanging around and vit. C tablets are cheap so we say to use them. I would find a way (in a sock or such) to keep the ascorbic acid where you want it and can be removed if wanted needed. Make sure to brush REAL good once you are through.

Kim