SLAMMING my pool for black algae

[vickiejsmith]

I am currently doing my first ever SLAM on my pool for black algae, and have a few questions.

Would adding polyquat help speed up the process? I began last Wednesday night, getting my pool up to the slam level of 12. I have consistently been getting at least 2ppm FC loss during the night. Through reading on this site tonight, I see I need to consistently add chlorine throughout the day to keep the FC levels at 12 at least, as it has been dropping to about 10.5ppm by nighttime. I am seeing some of the black algae spots are starting to 'shred' and diminish, so I can see there has been some effect.

I have a gunnite/plaster pool that is at least 35 years old, and needs to be replastered, but it is simply not an option at this point. Am I correct in thinking that the SLAM process will be able to get the algae out of the nooks and crannies?

Do I need to take out the pool light for this?

I seem to have two kinds of black spots in my pool; the round black algae spots that are shredding, and smaller spots that are smaller than a pencil eraser, and do not scrape off with a trichlor puck. I have tried. I have attached two pictures of them.

This morning, FC was 13.5ppm, CC was 0; this evening FC was 10.5ppm and CC was 0. I have not tested for anything else since beginning the slam.

Last question; where on this forum do I create my signature with all my pool info?

Thanks,

Vickie
Houston, TX

28K IG plaster, 2HP 2 speed Pentair, cartridge filter 520sq ft, 150 gal/min flow rate Pentair, built 1984, dolphin deluxe 4, master temp 400 heater, spa

 

[Jeetyet]

To change your profile or signature, see the User Control Panel link, just below the TFP logo at the top of the forum. Then select the profile tab, and you can edit your location. Click on Edit Signature to change your signature.

From the following sticky...

http://www.troublefreepool.com/what-we-need-to-know-to-answer-your-questions-t10341.html

 

[linen]

Have you tested each type of black spot? If the inside is green, then it is black algae. If it is black algae, while you are doing the SLAM process, you need to break it's waxy protective layer so that the chlorine can kill.

Would adding polyquat help speed up the process?

No, algaecide is extra insurance to prevent algae, but once you have it chlorine is much better at killing it.

What is your cya level?

What are you using for your test numbers?

Am I correct in thinking that the SLAM process will be able to get the algae out of the nooks and crannies?

Yes, but it will require brushing often to get rid of any biofilms that might form in those crannies.

 

[vickiejsmith]

My test numbers when I started the slam last week were:

FC: .5ppm
CC; .5ppm
pH; 7.5
TA; 70-80
CH; 550
CYA; 30

I have been able to scrape the tops off some of the bigger spots, and they must be black algae, because they are as you describe. The other black spots are like in the pictures; very small, and I haven't been able to scrape anything off of them. I have tried with a trichlor puck. It just beat up the plaster and the spot was untouched.

 

[BoDarville]

FC: .5ppm, CC; .5ppm, CYA; 30

This combination is what allowed the algae to establish. Even with a good CYA level of 30 ppm, the FC should not drop below 2 ppm in order to avoid an algae outbreak.

The key to dealing with black algae is brushing along with elevated FC levels. You need to brush at least twice a day to break down black algae's protective coating.

Do I need to take out the pool light for this?

Yes. Here's what could be behind it: http://www.troublefreepool.com/think-i-may-have-found-my-fc-demand-issue-t65957.html

 

[vickiejsmith]

OK, I will take the light out and deal with that. I should have posted this in my introductory post, in which I describe how we took over caring for our pool in May from a pool care company. We kept having algae problems, just not black algae. Since taking over, we had not been able to maintain an FC level of 2. It kept going to zero fast. We finally found this site, and started the slam.

Did you see the pictures I posted? Is this black algae?

 

[BoDarville]

The pics sure look like black algae. To know for sure, scrape the spots. If the inside is green, then it is black algae. If not, try holding/rubbing a Vitamin C tablet on it for about a minute or two. If it lifts, then it is a metal stain. Over-spray from some lawn/plant fertilizers have been know to cause this type of spotting. Any chance this could have happened? If so, you could also have a mix of both black algae and metal staining. Focus on cleaning up the algae first.

I have consistently been getting at least 2ppm FC loss during the night.

Bottom line is that you have something organic in your pool if you are having trouble maintaining chlorine overnight. You need to continue The SLAM Process until you pass all three criteria listed in the SLAM article.

 

[vickiejsmith]

Thanks

 

[yishen]

Hi there,
Did you get rid off both black spots in the photos? I just moved in my first pool home and I have a lot of the small black spot in the pool.
Looks like you had in the pictures.

I had tried to see if they are black algae or stains, but none of that succeed.
Any experience you could share would be much appreciated!!