adamopc123

Member
Aug 21, 2022
7
Huntsville, Alabama
Pool Size
17000
Surface
Vinyl
Chlorine
Salt Water Generator
SWG Type
Hayward Salt & Swim 3C
I’m struggling with a mysterious battle of what appears to be standard green algae, but I guess could be mustard algae.

I transitioned from a single speed pump to a VSP back in early August. A few weeks later, I realized I had small clouds of greenish/brownish residue that would be visible when lightly brushing the bottom of the pool. I performed an OCLT and showed no loss, but decided to SLAM anyway. I completed my SLAM 4 days later with absolutely crystal clear water and no residue remaining. I washed my cartridge filter 3 times during the SLAM. My OCLT passed every night during the slam, but I keep it up until all cloudiness in my water had disappeared.

I’ve enjoyed amazingly beautiful water for a month since that SLAM. I have checked FC every day and it has not dropped below 6.5ppm in the entire month. However, I’ve just noticed the return of these green clouds on the bottom of the pool when brushing. My water appears this evening to be ever so slightly cloudy when looking in my pool light’s glow.

I have tested CYA at 60-65ppm. I have SWG running to keep FC steady, with the SWG running at roughly 20% capacity. My VSP is running medium speed (2200 rpm) for 8 hours a day and low speed (1700rpm) 6 hours a day, for a total of 14 hours of filtration. This equates to 3 total water exchanges a day in my setup.

Why on earth would I be seeing a return of this algae after a month in these conditions?
 

adamopc123

Member
Aug 21, 2022
7
Huntsville, Alabama
Pool Size
17000
Surface
Vinyl
Chlorine
Salt Water Generator
SWG Type
Hayward Salt & Swim 3C
I’m battling a very similar situation with this “dust” on the bottom of the pool. I performed a 4-day SLAM and it went away, but has now returned a month later. I never went to mustard algae levels because I thought it was standard green algae. Perhaps I was wrong? Is this “dust” something that points to mustard algae?
 

PoolStored

Gold Supporter
TFP Guide
Jun 24, 2021
3,169
Ashtabula, OH
Pool Size
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Surface
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Chlorine
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SWG Type
CircuPool RJ-60
@adamopc123 Welcome to TFP!!!

  1. How often do you brush your pool?
  2. When, exactly, during the 24 hour cycle, relative to your 8 hour medium speed, 6 hour Low speed, and 10 hour rest cycle? i.e. "8 hour cycle starts at 8pm, followed by 6 hour and 10 hour, and I test at 4pm."
  3. What is the shape and depths of your pool, how many returns do you have and where are they placed?
 

adamopc123

Member
Aug 21, 2022
7
Huntsville, Alabama
Pool Size
17000
Surface
Vinyl
Chlorine
Salt Water Generator
SWG Type
Hayward Salt & Swim 3C
@adamopc123 Welcome to TFP!!!

  1. How often do you brush your pool?
  2. When, exactly, during the 24 hour cycle, relative to your 8 hour medium speed, 6 hour Low speed, and 10 hour rest cycle? i.e. "8 hour cycle starts at 8pm, followed by 6 hour and 10 hour, and I test at 4pm."
  3. What is the shape and depths of your pool, how many returns do you have and where are they placed?
1. Not especially often except during the slam. I run my Dolphin M400 a couple of times each week and it climbs all my walls.

2. 7-8 am is low speed; 8am-12pm medium speed; 12pm-4pm low speed: 4pm-8pm medium speed; 8pm-9pm low speed. Rest from 9pm-7am.

3. Freeform shape but essentially a kidney. 40” deep on shallow, 5’8” on deep end. 1 return on shallow end opposite skimmer. 2 returns on deep end, one opposite the skimmer and one down low to stir up the deep water. I do not have a main drain. All returns are oriented to keep the water rotating and are hardly disturbing the surface at all when running at medium speed or below. At high speed, I get significant turbulence.

These issues really began when I switched to VSP, so I think it is something to do with my circulation. I spent 18 months without this issue happening with my old pump and now I’ve had it twice in 2 months. At 2200rpm, my two skimmers have good suction and I’m showing roughly 60gpm on my flow meter. I have assumed this is enough due to the movement I can see in the water, but perhaps I’m wrong.
 

adamopc123

Member
Aug 21, 2022
7
Huntsville, Alabama
Pool Size
17000
Surface
Vinyl
Chlorine
Salt Water Generator
SWG Type
Hayward Salt & Swim 3C
Sorry I was not clear. What time of the day do you test?

Oh - my apologies.

I usually test at either 8am or 6pm. Most often it is at 6pm. I try to get elbow deep samples from a section of the pool between the returns so I’m not getting freshly chlorinated water from the SWG.
 

PoolStored

Gold Supporter
TFP Guide
Jun 24, 2021
3,169
Ashtabula, OH
Pool Size
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Surface
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Most often it is at 6pm.
I vote that your FC got low. At 6pm, you are testing AFTER your SWCG has added the majority of the FC for the day, as it was running for 11 of the 14 hours. If it never got below 6.5 and you tested at 6pm, it could have EASILY dropped below 4 by 6/7 am.

I would recommend that you reprogram your VSP. I, like MANY others here, run it at low speed for 24 hours with SWCG to keep the FC even. Run your pump down in RPM until your "low flow" light comes on. Then add 100-200 RPMs. Run it at that speed 24/7. If you keep the right water level in your pool (1/2 way up skimmer opening), and have weir doors, you will get just fine skimming. You will also save a bunch on electricity.

When you test your CYA, do you test it in BRIGHT sunlight, with sun to your back, holding at your waste in the shade of your body? Or do you test indoors?
 
Last edited:

adamopc123

Member
Aug 21, 2022
7
Huntsville, Alabama
Pool Size
17000
Surface
Vinyl
Chlorine
Salt Water Generator
SWG Type
Hayward Salt & Swim 3C
I vote that your FC got low. At 6pm, you are testing AFTER your SWCG has added the majority of the FC for the day, as it was running for 11 of the 14 hours. If it never got below 6.5 and you tested at 6pm, it could have EASILY dropped below 4 by 6/7 am.

I would recommend that you reprogram your VSP. I, like MANY others here, run it at low speed for 24 hours with SWCG to keep the FC even. Run your pump down in RPM until your "low flow" light comes on. Then add 100-200 RPMs. Run it at that speed 24/7. If you keep the right water level in your pool (1/2 way up skimmer opening), and have weir doors, you will get just fine skimming. You will also save a bunch on electricity.

When you test your CYA, do you test it in BRIGHT sunlight, with sun to your back, holding at your waste in the shade of your body? Or do you test indoors?
Thanks so much for all the feedback so far.

Maybe I’ve had some poor assumptions on the FC behavior overnight. I thought overnight loss in a properly maintained pool would be very minimal. At 6.5ppm at 6pm, I still have 3 hours of chlorine generating time left. I thought it would be good overnight as long as I was above my “target” level at sunset. Is that not the case?

I’ve attempted to run longer with low flow like you suggested, but I found that I struggled with pool debris. I have a lot of trees nearby and windy days can be rough without fairly significant flow towards the skimmers. I can find a better balance though.

On CYA testing, I do it outdoors as you described. Bright sunlight with my body shading the test sample and holding it at waist height.

Is it possible that this green “dust” on the bottom is actually mustard algae? My SLAM log from a month ago is below. I’m wondering if I perhaps didn’t kill everything and it took several weeks for a resurgence. I never went to mustard SLAM levels.

8/19
7:00am - 19.5 FC, 0ppm CC
9:15am - 17ppm FC
10:30am - 25ppm FC
11:30am - 22ppm FC
12:40pm - 26ppm FC
5:08pm - 26.5ppm FC
7:45pm - 27.5ppm FC

8/20
6:30am - 26.5ppm FC
6:21pm - 21ppm FC

8/21
6:55am - 24ppm FC
6:30pm - 18ppm FC
8:16pm - 30.5ppm FC

8/22
6:00am - 30ppm FC / 0.5ppm CC
5:20pm - 22.5ppm FC / 0ppm CC
 

PoolStored

Gold Supporter
TFP Guide
Jun 24, 2021
3,169
Ashtabula, OH
Pool Size
30000
Surface
Vinyl
Chlorine
Salt Water Generator
SWG Type
CircuPool RJ-60
Thanks so much for all the feedback so far.
No worries.
Maybe I’ve had some poor assumptions on the FC behavior overnight. I thought overnight loss in a properly maintained pool would be very minimal. At 6.5ppm at 6pm, I still have 3 hours of chlorine generating time left. I thought it would be good overnight as long as I was above my “target” level at sunset. Is that not the case?
You would be surprised. All it takes is a whiff of minimums and my pool clouds.
I’ve attempted to run longer with low flow like you suggested, but I found that I struggled with pool debris. I have a lot of trees nearby and windy days can be rough without fairly significant flow towards the skimmers. I can find a better balance though.
Sooooo...run 24/7. Run at the low end (flow switch +200) for the majority of time, then run higher when you need to skim. It is all about running the pump for a reason. Skimming, chlorinating, vacuuming, filtering, etc. If you have a need to skim, run some period of the 24hrs at "skim speed," for your needs!
On CYA testing, I do it outdoors as you described. Bright sunlight with my body shading the test sample and holding it at waist height.
Great! If you do it in low light, or indoors, it will read low. Just wanted to make sure your CYA wasn't in fact higher, necessitating a higher FC.
Is it possible that this green “dust” on the bottom is actually mustard algae? My SLAM log from a month ago is below. I’m wondering if I perhaps didn’t kill everything and it took several weeks for a resurgence. I never went to mustard SLAM levels.
Likely not, given your description. Given that it was "gone" for a period of time, you killed it. Your FC just got low again and you got algae.
8/19
7:00am - 19.5 FC, 0ppm CC
9:15am - 17ppm FC
10:30am - 25ppm FC
11:30am - 22ppm FC
12:40pm - 26ppm FC
5:08pm - 26.5ppm FC
7:45pm - 27.5ppm FC

8/20
6:30am - 26.5ppm FC
6:21pm - 21ppm FC

8/21
6:55am - 24ppm FC
6:30pm - 18ppm FC
8:16pm - 30.5ppm FC

8/22
6:00am - 30ppm FC / 0.5ppm CC
5:20pm - 22.5ppm FC / 0ppm CC
Here is my best advice:
1) SLAM again. You were right to continue SLAM until the water is clear...this includes living or DEAD algae not being present. This is the important part of "clear water."
2) Run your dolphin daily. I leave mine in the pool 24/7 and run once a day. This will circulate the water AND brush your pool, if you don't like doing it. Helps with any dead circulation areas. I really don't think it is circulation. I still think it is allowing FC to get too low.
3) Adjust your pump and SWG to run 24/7, running higher to skim as necessary. Adjust your SWCG % for the 24 hour run, you do not need to adjust % for pump speed, SWCG is either on or not.
4) Run your FC higher. The pool is safe to swim up to SLAM levels. I keep 70ppm CYA. FC/CYA Chart says my minimum is 3 and target is 5. I keep mine at 8-9. Allows me to have a big demand day (sometimes in June/July up to 5FC demand) and not worry about getting to minimums.
 

adamopc123

Member
Aug 21, 2022
7
Huntsville, Alabama
Pool Size
17000
Surface
Vinyl
Chlorine
Salt Water Generator
SWG Type
Hayward Salt & Swim 3C
No worries.

You would be surprised. All it takes is a whiff of minimums and my pool clouds.

Sooooo...run 24/7. Run at the low end (flow switch +200) for the majority of time, then run higher when you need to skim. It is all about running the pump for a reason. Skimming, chlorinating, vacuuming, filtering, etc. If you have a need to skim, run some period of the 24hrs at "skim speed," for your needs!

Great! If you do it in low light, or indoors, it will read low. Just wanted to make sure your CYA wasn't in fact higher, necessitating a higher FC.

Likely not, given your description. Given that it was "gone" for a period of time, you killed it. Your FC just got low again and you got algae.

Here is my best advice:
1) SLAM again. You were right to continue SLAM until the water is clear...this includes living or DEAD algae not being present. This is the important part of "clear water."
2) Run your dolphin daily. I leave mine in the pool 24/7 and run once a day. This will circulate the water AND brush your pool, if you don't like doing it. Helps with any dead circulation areas. I really don't think it is circulation. I still think it is allowing FC to get too low.
3) Adjust your pump and SWG to run 24/7, running higher to skim as necessary. Adjust your SWCG % for the 24 hour run, you do not need to adjust % for pump speed, SWCG is either on or not.
4) Run your FC higher. The pool is safe to swim up to SLAM levels. I keep 70ppm CYA. FC/CYA Chart says my minimum is 3 and target is 5. I keep mine at 8-9. Allows me to have a big demand day (sometimes in June/July up to 5FC demand) and not worry about getting to minimums.
I’ll get to work on the new SLAM. I appreciate all the advice. This new VSP has been a new learning curve for me, but the electricity savings will be really great once I tune it in and get past the need to keep buying SLAM bleach!

This website has been an amazing education resource. I had no idea just how clear my water could be until I completed my first SLAM. I literally gasped when I saw my pool light on with truly clear water for the first time.
 

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PoolStored

Gold Supporter
TFP Guide
Jun 24, 2021
3,169
Ashtabula, OH
Pool Size
30000
Surface
Vinyl
Chlorine
Salt Water Generator
SWG Type
CircuPool RJ-60
I’ll get to work on the new SLAM. I appreciate all the advice. This new VSP has been a new learning curve for me, but the electricity savings will be really great once I tune it in and get past the need to keep buying SLAM bleach!

This website has been an amazing education resource. I had no idea just how clear my water could be until I completed my first SLAM. I literally gasped when I saw my pool light on with truly clear water for the first time.
Yes. It just works. You just need to stay away from minimums. 24/7 will really help keep FC steady. Just run a higher FC. 45 Gallons of bleach for my one and only SLAM. Pool perfect once I understood my daily FC demand and just maintained a higher FC to never get near minimum. Use PoolMath tracking to figure out your FC demand by month and adjust. I run 15% June/July, 10% May/Aug/Sept. This is my baseline for pool with cover on. When we are going to swim, I turn it up to 50% when the cover comes off, and back to 15% when cover goes back on in June/July, and boost to 30% in the shoulder months when cover comes off and back to 10% when cover goes back on. Keeps my FC right where I want it. You will learn your pool. You will be good!

I ran my pump 3450 RPM 24/7 the first year...Sheesh. Now I run 1400 24x7. 150 Watts +/-. I do use a solar cover which really helps with the debris. On the pump schedule, start by trying 4 hours in the late afternoon, maybe 2000-2200 to get your skimming done. Do you use hair nets? They are the nutz!
 

adamopc123

Member
Aug 21, 2022
7
Huntsville, Alabama
Pool Size
17000
Surface
Vinyl
Chlorine
Salt Water Generator
SWG Type
Hayward Salt & Swim 3C
Yes. It just works. You just need to stay away from minimums. 24/7 will really help keep FC steady. Just run a higher FC. 45 Gallons of bleach for my one and only SLAM. Pool perfect once I understood my daily FC demand and just maintained a higher FC to never get near minimum. Use PoolMath tracking to figure out your FC demand by month and adjust. I run 15% June/July, 10% May/Aug/Sept. This is my baseline for pool with cover on. When we are going to swim, I turn it up to 50% when the cover comes off, and back to 15% when cover goes back on in June/July, and boost to 30% in the shoulder months when cover comes off and back to 10% when cover goes back on. Keeps my FC right where I want it. You will learn your pool. You will be good!

I ran my pump 3450 RPM 24/7 the first year...Sheesh. Now I run 1400 24x7. 150 Watts +/-. I do use a solar cover which really helps with the debris. On the pump schedule, start by trying 4 hours in the late afternoon, maybe 2000-2200 to get your skimming done. Do you use hair nets? They are the nutz!
I shouldn’t have any issue keeping a higher FC as my SWCG was only running at about 10% capacity when I was at 6.5ppm. My only real reason for keeping FC closer to the “target” of 4 is in an attempt to prevent premature liner fading by consistently keeping high FC.

Those hair nets look like a great idea! I’ll have to try that.
 
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