Black Algae - doing SLAM - questions

[CountyBumkin]

My pool has a lot of Black Algae. I guess I didn't pay enough attention to the pool chemistry, and now I have to deal with it. Usually I'll get some green algae in the summer months and its easy to brush away.

I have been doing the SLAM (My FC is at 24 and CYA is 70). It's been three days now. I added about 5 lbs of shock to start with (box says to use 1lb per 12,000 gallons). I'm not sure how much water my pool holds - I think around 20,000 gal.
But the whole box got me up to 24ppm FC. yesterday I had to add 2 lbs more. I'm also running the pool's SWG 24hrs a day at max for the duration, and I have a floating dispenser with a puck in it. Part of the problem is the heavy rain storms every afternoon diluting the chlorine and the strong sun trying to break it down (I'm in FL). I also added some more chlorine stabilizer yesterday.

My numbers are:
FC 24
CC 0.5 (maybe zero)
ALK 100
CAL 140
I did not test Salt level, but the SWG (IntelliChlor40) display shows the salt level is good.

So the SLAM Chlorine level looks good. But I cant get rid of the Black Algae. I think some has gone (at least the two steps are looking better) but not much change elsewhere. It's real hard work to push those (6" wide) stainless steel brush around the pool ( I feel like I'm shoveling snow). My arms and shoulder are hurting now - but that is part of the joy of pool ownership.

Questions:
1) Do I need to get all the Black Algae out? If I get 80 - 90% out, and then maintain 4 to 5 ppm FC, is that good enough or will the Black Algae continue to grow?
2) I am brushing over and over the same spots but they don't come up. Is it correct to assume that I have "broken" the waxy shell of the Algae and I just need to let the chlorine do its job now? Or should I be able to completely brush away the black spots?
3) Do I need to remove the pool lights to get in the light shell? I don't know if there is any Algae behind the lights. I don't see any algae on the pool walls or around the light fixtures.

 

[Katodude]

I feel your pain. I just caught some black algae in my pool, fortunately I caught it early. Here is what I did, and an expert will chime in shortly to give you more complete advice. Do you have a plaster or pebble pool? If so get a wire brush and really go at those spots. I wore a mask and snorkel and dove down to really scrub them. I also took a little bamboo bbq skewer that really let me pick at the spots to pull out algae. I would pull out the lights and clean behind them. I am keeping the pool at SLAM level for a while and go back in daily to keep scrubbing those spots with the wire brush (at this point where the spots were since I got all the algae up).

Its a slog but so far its working for me.

Oh, I also used a 1” PVC tube to super dose the spots to make sure I kill everything.

I plan on keeping an elevated FC level for several weeks and continue to scrub at the old spots. I never want to see this stuff again.

 

[CountyBumkin]

My pool is gunite/concrete (plaster).
Do I need to scrub the spots until gone - or am I just trying to break the "waxy coating" so the Chlorine can kill it? - which would mean it would die and disappear sometime later.
And it's not just one spot. These black spots are all over the pool. I'll see if I can post a photo.

 

[Katodude]

Ok, lets back up for a second. First how are you testing your water? Second get all the pucks out of the pool, adding stabilizer at this point is not good. 3rd stop using powder for chlorine. Go get LOTS of liquid chlorine.

So it looks like you have lots of black algae. You will need to scrape that up. You have a stainless steel brush, keep using it. I actually take mine off the pole and get into the pool with a mask and snorkel and scrub by hand. The pole just does not give me enough leverage. The “waxy coating” is pretty thick on black algae. It also re forms fairly quickly. So If you just scrape off the top layer, you will need to do that again, and again, and again, until it is all gone. Also for the amount that you have I would think you need your pool at SLAM level which is a FC of 28. Once all the spots are gone then you can maintain a FC level of 12 -14 for a few weeks to make sure you got it all.

One thingI have done before I refinished my pool and did not care as much about the finish is I have gone into the pool with a pressure washer and used that to pop the black algae out. Remember this is a high risk manuver since you can damage your plaster further this way.

 

[setsailsoon]

County,

Sorry to hear about your problems with black algae. Like Kato, I have much better luck by gentle scrubbing with a mask and hand brush. Did you lower pH before you started the SLAM? Can you please confirm how you are testing? Also, SLAM uses liquid chlorine not granular shock and your chlorinator should be off. This may help.

Chris

 

[CountyBumkin]

Thanks for the help.
I'm testing with the Taylor 2006C kit.
I did not lower pH (I thought I was supposed to be sure it was in the "normal range" before starting the SLAM). It is (was) around 7.6 when I started.
Regarding liquid chlorine. I started with 9 gallons of bleach. That was all I had, and it was not enough to get FC above 14ppm. You can't buy more than 2 gallons of bleach at a time now - so I had to go with the granular shock kind.
The SLAM instructions say to run the pump/filter 24/7 during this process. Should I disable the SWG (unplug the Intellichlor)? I'm running the pump now in "SuperChlor" mode which is 100% output. I assumed this would help keep the chlorine levels high.

 

[setsailsoon]

Thanks for the help.
I'm testing with the Taylor 2006C kit.
I did not lower pH (I thought I was supposed to be sure it was in the "normal range" before starting the SLAM). It is (was) around 7.6 when I started.
Regarding liquid chlorine. I started with 9 gallons of bleach. That was all I had, and it was not enough to get FC above 14ppm. You can't buy more than 2 gallons of bleach at a time now - so I had to go with the granular shock kind.
The SLAM instructions say to run the pump/filter 24/7 during this process. Should I disable the SWG (unplug the Intellichlor)? I'm running the pump now in "SuperChlor" mode which is 100% output. I assumed this would help keep the chlorine levels high.

OK that's good. Just wanted to be sure I know where you are in the process. Where are you getting your bleach and what brand is it? You can get bulk chlorine at all Leslie's, Pinch a Penny, and Pool Marts in FL. It's by far the cheapest and ranges 10-10.5%. There is also no limit on it. You do need the containers but you are not adding CH or CYA to keep your chlorine level up. If CH or CYA get too high it can require you drain water. I usually get 5 gal for $7.99. Bought some last week. You should turn off the chlorinator so you can accurately tell how much FC is being consumed during your SLAM.

I hope this helps.

Chris