Help with SLAM for mustard algae

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srwdvm

Member
Jul 18, 2024
8
Austin, TX
Hi there,

I’ve been browsing similar posts and I suppose I just need support to know I’m on the right track.

I’ve just completed day 7 of SLAM. On 4 of those days (including first 3 days), I was off work and checked levels and added chlorine 6-7 times a day. On 3 days I worked and could only do 4 times a day.

90% of the visible algae cleared up in the first 48 hr but there has been a plateau and I have observed the same amount accumulating every day for about the last 4 days.

There is consistently a 2-4 point drop in my Cl overnight, as expected with visible algae.

I’m using 10% LQ and following Pool Math for dosing instructions. I’m getting in to brush at almost every Cl check. Running the pump 24/7, as I always have. CYA is 50.

My stairs are hollow and removable. I spray bleached them at the beginning. Since then I have brushed them and drained them several times a day, letting them refill with the high Cl- SLAM water.

I know SLAM is supposed to be safe for vinyl pools but I’m worried that my liner is looking so bleached. I’m worried that I haven’t seen any progress since the early days.

I mentioned in my introductory post that I have a tree shading most of my pool which daily adds organic debris including leaves and lots of caterpillar and animal droppings. My water temp averages about 93 degrees and runs through a solar heating system. The response to that post said thesethings should not influence the success of my SLAM.

MY water was clear and balanced at the start, not swampy and gross, so I was not expecting it to take this long.

So, any recommendations, or just stay the course? Apparently, there is no such thing as a SLAM failure but I am feeling gloomy.
 
srwdvm said:
Hi there,

I’ve been browsing similar posts and I suppose I just need support to know I’m on the right track.

I’ve just completed day 7 of SLAM. On 4 of those days (including first 3 days), I was off work and checked levels and added chlorine 6-7 times a day. On 3 days I worked and could only do 4 times a day.

90% of the visible algae cleared up in the first 48 hr but there has been a plateau and I have observed the same amount accumulating every day for about the last 4 days.

There is consistently a 2-4 point drop in my Cl overnight, as expected with visible algae.

I’m using 10% LQ and following Pool Math for dosing instructions. I’m getting in to brush at almost every Cl check. Running the pump 24/7, as I always have. CYA is 50.

My stairs are hollow and removable. I spray bleached them at the beginning. Since then I have brushed them and drained them several times a day, letting them refill with the high Cl- SLAM water.

I know SLAM is supposed to be safe for vinyl pools but I’m worried that my liner is looking so bleached. I’m worried that I haven’t seen any progress since the early days.

I mentioned in my introductory post that I have a tree shading most of my pool which daily adds organic debris including leaves and lots of caterpillar and animal droppings. My water temp averages about 93 degrees and runs through a solar heating system. The response to that post said thesethings should not influence the success of my SLAM.

MY water was clear and balanced at the start, not swampy and gross, so I was not expecting it to take this long.

So, any recommendations, or just stay the course? Apparently, there is no such thing as a SLAM failure but I am feeling gloomy.
Click to expand...
Post your latest complete test results.
 
FC = 17 at 7:30 pm (had been 14 at 4 pm), added recommended amount of Cl
CYA = 52
Ph = 7.6
TA = 90

I hadn’t been checking the pH and TA regularly because I thought the readings were unreliable during SLAM, but I just checked them so I could reply to your post. Thanks for responding!
 
srwdvm said:
FC = 17 at 7:30 pm (had been 14 at 4 pm), added recommended amount of Cl
CYA = 52
Ph = 7.6
TA = 90

I hadn’t been checking the pH and TA regularly because I thought the readings were unreliable during SLAM, but I just checked them so I could reply to your post. Thanks for responding!
Click to expand...
How did you get 52 for CYA?
 
Good morning! My Cl reading this morning was just 15, the lowest overnight reading I have had so far:(

The test kit measuring device only has markings in increments of 10. The reading was about a quarter of the way between 50 and 60. Is there a better way to measure? I am using the Taylor test kit with reagent R-0013 where you look for the dot to disappear.
 
CYA is logarithmic - you cannot guess between the lines, so you need to always round up to next 10.

Stay the course, but 60 is your SLAM CYA level. It's also worth hunting for hidden areas a bit more; weir doors, those stairs, etc.
 
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Hi there,

So I am now 12 days into SLAM. I have been checking and adding Cl at least 4 times, and usually 6-7 times a day. I may have underestimated my CYA for the first several days, which may be why it has taken so long. The only part of the test I am still failing at is the OCLT. This morning my FC was 22 and CC was 0. My SLAM goal is 24, but my last check last night the FC was 25.5.

There is finally no visible algae!

As I’ve mentioned, my pool gets a lot vegetative debris and critter poop accumulate all day and overnight.

Is it possible that this stuff is also driving my Cl lower overnight so that I might never pass the OCLT?

I’m about ready to give up. I have hardly left my house in 12 days except work and my liner is looking very bleached.
 
srwdvm said:
Hi there,

So I am now 12 days into SLAM. I have been checking and adding Cl at least 4 times, and usually 6-7 times a day. I may have underestimated my CYA for the first several days, which may be why it has taken so long. The only part of the test I am still failing at is the OCLT. This morning my FC was 22 and CC was 0. My SLAM goal is 24, but my last check last night the FC was 25.5.

There is finally no visible algae!

As I’ve mentioned, my pool gets a lot vegetative debris and critter poop accumulate all day and overnight.

Is it possible that this stuff is also driving my Cl lower overnight so that I might never pass the OCLT?

I’m about ready to give up. I have hardly left my house in 12 days except work and my liner is looking very bleached.
Click to expand...
You should not go over the FC SLAM amount. It’ll make your OCLT more likely to fail. Not a big deal for one day but if it’s been doing that a lot, scale back your FC amounts so it stays closer to 24ppm. If it was a bad case of algae, 12 days isn’t unreasonable.
 
So first I was doing it wrong because I was not adding enough. Now I am doing it wrong because I am adding too much.

I did not intentionally go over. I added exactly the amount the Pool Math recommended.

I don’t know how to define “bad case of algae”. My water has always been clear and balanced. I just could never get rid of the mustard algae on the bottom.
 

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srwdvm said:
So first I was doing it wrong because I was not adding enough. Now I am doing it wrong because I am adding too much.

I did not intentionally go over. I added exactly the amount the Pool Math recommended.

I don’t know how to define “bad case of algae”. My water has always been clear and balanced. I just could never get rid of the mustard algae on the bottom.
Click to expand...
It’s ok. Just sounds like your pool volume is smaller than pool math thinks it is. Maybe add 500 gallons to the estimate and see how that works. You mentioned potential liner bleaching so I brought that up. General consensus is that staying under SLAM level isn’t going to bleach the liner.

Algae growing on the walls is bad enough but swamp level algae will take weeks. 12 days isn’t unusual though reading through all the SLAM posts lately.

Debris and poop will consume a bit of chlorine but unless it’s a deluge it’s probably minimal impact.
 
My recent slam took about 40 days give or take. But I’m golden now. Keep it up! Clean everywhere you can think of. Lights, weir doors, etc.
 
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