Black Algae - Store Scared Me

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GoGators

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May 27, 2016
22
Boca Raton, FL
First I want to say, I'm new to the pool thing and TFP has been fantastic!

I bought a house a few months ago with a freshly redone pool (Dec) and the pool has been relatively pain free. At first I thought we had aggregate pool but the more I read, the more I think we have a poorly finished plaster pool. We started with a pool guy that never showed so I gradually started to learn and now I'm taking care of it. I vacuum twice a week, brush 1-2 times a week, clean the filter twice a month, and run the filter 10 hours a day. A few weeks ago I noticed a few spots of black algae (7 spots) in some divots on the stairs so I dove under, scrubbed and scrubbed along with added 2.5 gallons of chlorine, per the pool store. They went away but now I'm seeing more and more spots, about 20-30 in the shallow end and want to take care of it.

My readings are below but the pool place said to just dump copper based black algae treatment in but from reading here, it seems I should bump my FC to 39, based on my CYA level. I've read I should brush numerous times a day, especially on the algae, and continuously test to maintain FC levels. I went to the pool store to get more liquid and they thought I was crazy so I'm thinking maybe I misread. I read threads that said the pool store was going to disagree but they really have me worried. I bought a metal pool brush but I'm holding off on adding Chlorine until I hear I'm correct or incorrect. The copper based treatment isn't real expensive but I hear it stains and such.

14-15k gallon Chlorine Pool
South Florida
TC - 4 PPM
FC - 4 PPM
Ph -7.8
Alkalinity -130 PPM
Calcium Hardness - 260 PPM
Stabilizer/CYA I believe - 100 PPM
Total Dissolved SOids - 1,100 PPM

I dump 1.5 to 2 cups of acid in a week to control pH, which they say is normal here, especially with a freshly done pool.
They wanted my stabilizer higher so I have floated 1-2 tablets a week.
Usually they say about 1.5 cups of acid but this week they are telling me 2.9 quarts, which seems high but maybe alkalinity?

Sorry, I know I'm being a noob and all this information is in the forum, which I have read but the store pretty much told me this was a terribly dangerous idea.
 
Sounds like your going to need to SLAM the pool but you'll need one of the recommended test kits -either the K2006 or TF-100 and and avoid the advice of the pool store. We can help you out from there

In short yes you will need liquid chlorine, if your CYA is 100 -that is high and you need to pull the tabs immediately and avoid putting any copper based products in your pool.
 
This is really confusing for new comers. It seems impossible that a professional service like a pool store could be so wrong when it comes to virtually everything about a swimming pool.

Important things to understand from a science point of view :

#1 - Hypochlorous Acid (HOCL) is what sanitizes your swimming pool. This is the active ingredient in ALL forms of "chlorine".

#2 - CYA removes hypochlorous acid from the water and sequesters it. The chlorine is then slowly released back into the pool as the hypochlorous acid gets used up. This protects your chlorine from the sun (that's good) but also protects the algea from the chlorine.

#3 - Very few pool professionals recognize just how little hypochlorous acid is left in the water when CYA is present. At CYA 100ppm and FC 39ppm - there is only 0.3ppm HOCL actually in the water.

3ppm FC with no CYA has significantly more HOCL in the water than 39ppm FC with 100ppm CYA.


0.07ppm HOCL is generally considered the number you need to keep algea from growing in the water.

At 100ppm CYA and 4ppm FC you are at 0.017ppm HOCL. Way way too low.


That and that alone is the source of your algae problem.


Science talk aside - you'll have to choose which direction to follow. Trying to do both is going to drive you crazy.
 
GoGators said:
They wanted my stabilizer higher so I have floated 1-2 tablets a week.
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And this is precisely why we pay no attention to pool store advice. Your CYA level of 100 as measured by the pool store is already too high, and that's assuming that measurement is correct, which is unlikely. CYA is the one thing that pool stores notoriously get wrong, and usually disastrously so. Furthermore, the test maxes out at 100, which means that your actual level could be much higher than that, even 3 to 4 times higher. The result is that whatever chlorine you add to the pool is mostly being rendered ineffective by the high CYA levels, and that's why you have algae.

The chlorine shock level is 40% of the CYA level, and it is safe to swim with FC up to that. So *if* your CYA is indeed 100 (or more), it would be perfectly safe to swim with FC up to 40 ppm.

The desired CYA level for a non-saltwater pool is 30-40, and for a saltwater chlorine generator equipped pool, 70-80 ppm. Unfortunately for you, a CYA level of 100 or more will make it almost impossible to achieve and maintain the necessary FC level to clear up your pool. So you are going to have to drain and refill with fresh water. How much depends upon what your true CYA level is, and to determine that you are going to need to obtain a good test kit. Either the TF-100 or K-2006 commonly promoted on this site will work. Until you can get a kit, add 1/2 gal of 8.25% bleach daily just to maintain where you are.

Only use chlorine bleach (regular unscented, not splashless) or liquid chlorine (same thing as bleach, but usually a stronger concentration) to raise your FC. Any other form of chlorine will also add undesirable things such as more CYA or calcium.

Then as Jezza noted, you are going to have to perform a SLAM to eliminate the algae for good. It sounds like you already have an understanding of what that entails.

Come back and post your results once you get your test kit and we'll take it from there. Good luck!
 
GoGators said:
... The copper based treatment isn't real expensive but I hear it stains and such. ...
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Welcome!

It's good that you didn't put it there- it would be impossible to remove but would lead to additional sales by pool store, still with no light at the end.

Please buy TF100 test kit instead and learn how to take care of your pool yourself: it's simple, it works and you'll save tons of money in very short time.
 
Wow, you guys are on top of it! Sorry, for what I'm sure is a non-stop repetitive post. I read, and read, thought I knew what I needed to do but the pool store threw me for a loop. I ordered the K2006 via amazon earlier today and was planning on going to the pool store 2-3 times a day to get testing done, until it arrived. I just pulled the tablets, which is funny, they keep telling me to float more :grrrr: As for the copper, I almost caved and just bought it because they were making me feel like a total idiot. They had all the employees come over and were basically saying, can you believe he wants to bump his FC that high, only a tad bit nicer. I'm sure they talked about me when I left and what an idiot I was but glad I didn't add copper. The one guy said don't worry, as you loose water from rain flooding it and evaporation, the cooper will disappear so you will need to add more. I asked if the evaporation would cause the cooper levels to lower and when he said yes, I asked, so copper evaporates and knew I may not being talking to the most intelligent people but still made me worry.

Thank you, thank you for all your help and I will post updates, just wish my CYA wasn't so high because it sounds like it will stay there for a bit.
 
GoGators said:
Wow, you guys are on top of it! Sorry, for what I'm sure is a non-stop repetitive post. I read, and read, thought I knew what I needed to do but the pool store threw me for a loop. I ordered the K2006 via amazon earlier today and was planning on going to the pool store 2-3 times a day to get testing done, until it arrived. I just pulled the tablets, which is funny, they keep telling me to float more :grrrr: As for the copper, I almost caved and just bought it because they were making me feel like a total idiot. They had all the employees come over and were basically saying, can you believe he wants to bump his FC that high, only a tad bit nicer. I'm sure they talked about me when I left and what an idiot I was but glad I didn't add copper. The one guy said don't worry, as you loose water from rain flooding it and evaporation, the cooper will disappear so you will need to add more. I asked if the evaporation would cause the cooper levels to lower and when he said yes, I asked, so copper evaporates and knew I may not being talking to the most intelligent people but still made me worry.

Thank you, thank you for all your help and I will post updates, just wish my CYA wasn't so high because it sounds like it will stay there for a bit.
Click to expand...

I would recommend to spare yourself a trouble and not to go to the store for testing, it doesn't sound like they know what they are doing. The only way copper can leave your pool is with water while draining the pool. There could be other losses due to spalsh out or intentional drain to prevent flooding but that's it. It will take months if not a year to come down to sensible level. You're correct copper and other dissolved solids do not leave pool due to evaporation: water evaporates while the rest remains in the pool.

Since we don't have any clue about your actual levels including CYA I'd just add 3/4 gal of 8.25% bleach daily to your pool until your test kit arrives and you'll be able to post actual numbers. BTW, my own CYA used to be 300 and I didn't have an option to do partial water replacement, still managed to get through, it's not that difficult.

Meanwhile you can do some background reading: ABC of Pool Water Chemistry so you'd be ready when the test kit arrives
 
So after mentally planning to drain half my pool, I found last weeks Pinch a Penny print out and found that today they told me my CYA level was 100 but yet on the 5th, they told me it was 60. I can't find other print outs right now but I swear it has been around 50 so maybe I'm not that bad off. I've added about 1 to 1.5 gallons of chlorine a week and it sounds like if my CYA level was indeed 100+, I would be adding more, correct? I didn't float tablets last week because Amazon lost my order so unless I'm wrong, there is nothing that could have raised my CYA from 60 to 100 in 5 days, right? I use Pinch A Penny Chlorine but that doesn't have CYA from my reading, correct? I have added nothing else in, minus chlorine.

Can't wait for a real test kit (I have a crappy $15 one) so I don't have to rely on the store because I am NOT happy with them right now. One morning I took my water to Miami because the stores weren't open yet and while I know I should have them test right away, I just needed acid and not a test but they told me my dissolved solids were 9,000 and when I questioned that, they said not to worry.
 
The inconsistency in your CYA readings are indicative of why we don't trust pool store readings. Liquid chlorine and bleach only add chlorine and a bit of salt. All solid forms of chlorine add either calcium or CYA depending on the product. This is why we generally promote the use of LC over other forms. It is much more manageable.
You'll be in the box seat when your proper test kit arrives and can gain control over your pool.
 
Look what came last night and wow, you guys were correct, the pool store was way off. I read the majority of the book and did all the tests twice, just to be safe and this is what I found:

PH - 7.7
TA - 90
CH - 300
CYA - 50 (perhaps 51)
10mL Test
FC - 6
CC - .5

25mL Test
FC - 5.6
CC - .4

The black algae seems to have gotten a bit better but I still see a few spots, which makes sense based on my low FC (which was lower last week), correct? Ideally, I would maintain a FC level of 6 and to kill the algae, I would maintain a 20 for about a week or until it disappears, yes?

Thank you all soooo much!

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Awesome! You are on the right path.

Now you can see why we make fun of pool store numbers :) Man they suck.

"TDS 9000" - unless your pool water tastes really salty I think that is silly. Regardless - it doesn't matter. TDS doesn't really tell you anything.

Your numbers actually look really good. Black Algae can be a pain - but with a little scrubbing and the proper level of Chlorine you'll beat it.
 
Thank you all again. I spent around an hour or so, diving down and scrubbing the dark spots off and then started the slam'ing process. I dropped my pH down a bit more, 7.4 because I read it was going to be hard to control/read with so much chlorine. I went a bit over my target at 24 FC but after a few days, I'm keeping it right around 20 and wow, the pool has never looked better! Last night I dropped from 20 to 18 so I'm getting there, loosing a lot less every night and throughout the day.

Thank you all so much, now on to reading up on removing a small rust spot on the bottom and some build up on the tiles.
 
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