Black algae

[ProspectHill]

Hello.
I noticed some clusters of black ‘freckles‘ on the bottom of the plaster pool.
I brushed with a nylon/wire combo brush and it wasn’t helping.
I had to leave for a month and the pool cleaner took over for me.
He told me the pool developed a green color and he shocked it and next day it looked fine.
when I returned there were a lot more black freckles.
I raised the chlorine level to 5. ( I’m in the Virgin Islands where people like to keep the chlorine level between 3-5 due to lots of direct sun.)
after reading some forum posts here, I tested a scraping of some spots and they did leave a green trail on the white paper.
The brush wasn’t enough so I put on a snorkel mask and used a small, hand held wire brush and scrubbed each spot one by one.
it worked very well. (The hardest part was staying submerged long enough to scrub more than one spot.)
i will have to go back and get some missed spots, but they all come off and I have some lose ‘blackheads’ in the water.

my taylor drop test numbers:
PH 8
FC 5
TC 3 I don’t understand why I often get a lower number for TC. Maybe regents are expired.
CC -2 This neg number happens often.
ALC 80
CH 50 ( or is that 500?)
CY 55. dont know how accurate this is, I tested twice and got btwn 53 and 55. It’s hard to know if that black dot is gone .

I’ll bring down the PH.
Are there next steps after that?

thank you, as always, for your advice.

Marcia

 

[mknauss]

With a CYA of 60, you should hold the FC at or near 12 ppm for an extended time to try and eradicate the black algae. Continued scrubbing of the areas will be needed.

Read Black Algae

 

[mknauss]

I would suggest getting a proper test kit. See Test Kits Compared

 

[ProspectHill]

With a CYA of 60, you should hold the FC at or near 12 ppm for an extended time to try and eradicate the black algae. Continued scrubbing of the areas will be needed.

Read Black Algae

Thank you.

Is it ok to stand in the water at that high a chlorine level?
It’s MUCH easier and more effective to scrub the pool while standing in it.

 

[proavia]

It's safe to swim anytime the FC is between minimum and SLAM Process level for your CYA and you can see the bottom of the pool.
See the FC/CYA Levels for FC levels based on your CYA.

What Taylor test kit are you using? Add it to ypur signature.
Test Kits Compared

 

[ProspectHill]

K-2005

 

[ProspectHill]

According to the test kit compare link:

”So if you already have the K-2005, go to tftestkits.net and order the FAS/DPD which converts your K-2005 to a K-2006 test kit.”

 

[proavia]

The FAS-DPD kit is the Taylor K-1515
You can also order the reagents thru TFTestkits as the 'SLAM Option' and get the powder scoop also.

 

[ProspectHill]

I’ll try that.
Can’t always get things in the VI
I’ll look to order it

Thank you again

 

[proavia]

Yeah, it may be a challenge to get one or one sent to the USVI.
Maybe you can order one on Amazon?
Let us know the outcome.

 

[Katodude]

My trick lately for removing the blackheads is to use a light pressure washer. I go in with a mask and snorkel and hit them. Or if you only have a few, use a bamboo BBQ skewer.

Go get a 1 gallon pump sprayer. Fill it with the strongest LC you can find and go spray the spots that you picked out. It will help kill the roots.

 

[ProspectHill]

So far the hand held wire brush is doing the job. There are not many spots left, and those are no longer black, but a dark green.

 

[ProspectHill]

Yeah, it may be a challenge to get one or one sent to the USVI.
Maybe you can order one on Amazon?
Let us know the outcome.

I ordered it from Amazon. I had to use a mainland account and it’s a 10$ delivery and a month wait.

 

[ProspectHill]

At the start of this my SWG was set at 40%. the FC was 2.
I turned it up to 60%, the FC rose to 5. To get it to SLAM level 12 I turned it up to 100%.
but my pump does not run 24/7. It’s only 8am - 6pm. I try not to drain my solar batteries all night. I have floated one chlorine puck to compensate for that.
does that make sense?

 

[ProspectHill]

Also, should I drain some water and add more to dilute the CYA ?
it’s high at 55.
thinking it won’t take so much chlorine then.
?

 

[mknauss]

Can you obtain liquid chlorine or plain bleach? The SWCG nor the trichlor will do what you need.

You can drain some water. You will then need to add some salt.

 

[ProspectHill]

Oh! Shoot. Around how much bleach?
ordinary Clorox bleach?

 

[ProspectHill]

I can get regular Clorox bleach this evening…then use it in the morning. Do I then set the SWG back from 100% to 0% while this process is happening?
I have 3 gallon sprayer if I should spray the bleach on the surface, as suggested by Katodude, but it’s just a dispenser, not a power spray.

 

[ProspectHill]

I have bags of salt on hand if I dilute the water.
is that something I should do? Reduce the CYA…would that be helpful?

if it’s not very important I would prefer not to.
I get water from my cistern and we haven’t had much rain lately. Even with hurricane Lee passing north, still gave us no rain.

 

[PoolStored]

Reducing CYA would be helpful, but not necessary.

Do not use chlorox brand bleach. It contains polymers. You want plain BLEACH. No splashless, no fragrances, no softeners...no nothing.