Black algae or metal stain

[Crazziee]

Hi,
I am a complete newbie to the pool. I purchased a house recently and it came with an in ground pool. The pool was filled but contained some yellow.

I cleaned the pool and the levels back in check. Now I have one issue that remains. I have these stains on my walls and I have no idea what they are. I am hoping its not black algae


https://lh5.googleusercontent.com/-3yZyb8tgkpw/Uzs-AJjRI9I/AAAAAAAAGeY/ye55lemfzTw/s800/GX079ug-ed.jpg
http://i.imgur.com.KILLED/GX079ug.jpg
https://lh3.googleusercontent.com/-JOje7Pp_WuU/Uzs-ALJbCTI/AAAAAAAAGeg/ry69scJO7JQ/s800/r1tSC2w-ed.jpg
http://i.imgur.com.KILLED/r1tSC2w.jpg
https://lh5.googleusercontent.com/-_TxSaS7EJPo/Uzs-BLX9-EI/AAAAAAAAGe0/lkk_ZQRGI3M/s800/vE0jbFq-ed.jpg
http://i.imgur.com.KILLED/vE0jbFq.jpg

[PoolDoc]

I looked at your pictures -- let me show you the color enhanced versions, which often reveals more relevant info:

#1:
https://lh4.googleusercontent.com/-SW1SKGhhc-k/Uzs-ANhkOHI/AAAAAAAAGeo/rXq2ygN2U2w/s800/GX079ug-ed2.jpg

#3:
https://lh5.googleusercontent.com/-VXptcyvBnjU/Uzs-BKNJmDI/AAAAAAAAGe4/a-C3YnEI5gQ/s800/vE0jbFq-ed2.jpg

#1 looks like thin plaster that has worn through, and exposed the underlying concrete / gunite.

#2 is uncertain.

#3 looks like possible black algae.

Here's what you need to do:

1. Purchase a cheap local OTO / phenol red drops kit and test your pool
2. If your pH is above 8.0 or below 7.0, post here immediately, with pool dimensions, for further instructions.
3. If your chlorine is zero, begin dosing with 1/2 gallon of plains 8% store-brand bleach* per 10,000 gallons of pool water, added each evening (NOT: morning or midday!)
4. Order a K2006 kit -- see kit info link in my signature -- from Amazon ASAP; report FULL readings here, including CYA, calcium hardness & alkalinity.
5. Meanwhile, operate your pump & filter 24/7

* If you've added copper based algicides, cut that to 1/8 - 1/4 gallon each PM . . AND . . tell us what you added (brand / maker / quantity / pool size).

[PoolDoc]

Hm-mm. Just processed your registration. Look up your address on Google Maps, satellite view.

If Google has your house ID'd correctly, dose your pool with 2 gallons of bleach each PM (or 1/2 gallon, if you've used copper). You appear to have a 16-20x40 modified rectangle with a deep end -- those usually run ~30,000 gallons

[PoolDoc]

Sorry if that sounds creepy -- but I use registration addresses + Gmaps to screen out spammers, before upgrading membership privileges.

[Crazziee]

Thanks for getting back so quick. Those modified images do show a better picture.
Before you responded I did a ph test earlier and it was off the scale, added some muriatic acid to lower.

Once that gets circulated I will take another check. Then update my results.

I am ordering a test kit right now.

Thanks again.

[Crazziee]

Kit ordered from Amazon, Should be here by Friday.

[Crazziee]

Hm-mm. Just processed your registration. Look up your address on Google Maps, satellite view.

If Google has your house ID'd correctly, dose your pool with 2 gallons of bleach each PM (or 1/2 gallon, if you've used copper). You appear to have a 16-20x40 modified rectangle with a deep end -- those usually run ~30,000 gallons

Thanks for checking it out. I have been wondering if the pool store misquoted me when they said it was about 44,000 gallons

[PoolDoc]

Actually dimensions will tell. It's worth measuring it!

And . . . what did the pH test show? Muriatic acid LOWERS pH levels; soda ash / washing soda or borax (Walmart detergent section) will RAISE it.

[Crazziee]

It was higher than my test kit, so over 8.

I will measure the pool now.

[Crazziee]

Wow I was way off. Its 32x16. Excluding the steps.

[PoolDoc]

Typically about ~20,000 gallons.

[Crazziee]

I am getting some bleach tonight after work. Should I still use 2 gallons a night? We estimated my pool to be around 20,000 gallons.

[PoolDoc]

If your pool is algae-free (except for the black algae), 1 gallon of fresh 8% store-brand bleach should be fine.

[Crazziee]

Ok, I added the 1 gallon of bleach last night. Should I add more this evening or wait on the Test kit?

Also does bleach contain Cyanuric acid?

thanks, again.

[PoolDoc]

+ Bleach contains no CYA.

+ Add 1 gallon of bleach EVERY evening, till you have the test kit.

[Crazziee]

Will do.

thanks.

[Crazziee]

Still waiting on the test kit.

I noticed my PH levels crept up again (of the chart). Would this be caused by the bleach?

[PoolDoc]

Only if your chlorine stays high.

Bleach raises the pH while it's present as free chlorine, but once the chlorine is 'used up', the pH effect from that individual dose of bleach disappears. Test with OTO (clear => yellow drops) purchased locally (Walmart!). If the chlorine is high (dark yellow or orange), skip chlorine doses and don't try to adjust your pH. If the chlorine is on scale with the OTO comparator (<5 ppm), go ahead and adjust your pH.

[Crazziee]

Still waiting on my test kit. Hoping it shows today.......

I am not seeing the black (algae) change color or begin to clear. Could it be that its metal related?

[PoolDoc]

To affect black algae, you have to (a) have high chlorine levels AND (b) brush the heck out of it.

[Crazziee]

Okay, I will up my brushing :)

=======================================

someone needs to invent a power brush with a spinning head, Would make my life easier...

[Watermom]

Look at the bright side ---- you will build up your muscles brushing! ;)

[PoolDoc]

Keep in mind, we haven't established that any of those spots ARE black algae. The most definitive test is to scrape some off with your fingernail, and smear it on a white card: black algae will smear dark green.

Brushing will make plaster wear through spots WORSE!

But, if you DO have black algae, a brush like this
Pentair R111616 604A Algae Brush with SS Bristles, 6-Inch (http://www.amazon.com/exec/obidos/ASIN/B006H48XXY/scouscho-20)will help.

http://ecx.images-amazon.com/images/I/416kynvDCGL._SY355_.jpg

NOTE TO OTHER READERS: Do *NOT* use a metal bristle brush on fiberglass or vinyl pools, EVER!