Algae in 8ppm FC?

pb4uswim

Well-known member
Jul 23, 2020
328
Michigan
I saw something I believe is algae in my pool last evening. I brushed it away with my foot and the area this morning has what appears to be a small indication of the algae reforming. I'm good with doing a SLAM but my question is - what the heck kind of algae grows in high chlorine levels? I've been monitoring my FC at lease every other day and for many weeks now it has never been below 6ppm and typically is over 8ppm. Last night, before I saw the algae, my measurement was 9ppm. I guess this could be pollen or dirt, but it was pretty green. Note, my CYA is 60 so according to the CYA chart, my target is 4ppm. I leave my pump running 24/7 and the SWG on 30% and I measure in the heat of the day. I just don't see how I've ever been at a chlorine level that would allow algae to grow. Any ideas?
 

Orion7319

Well-known member
Jul 1, 2020
550
Rock Hill, South Carolina
Pool Size
19775
Surface
Vinyl
Chlorine
Salt Water Generator
SWG Type
Hayward Aqua Rite (T-15)
I saw something I believe is algae in my pool last evening. I brushed it away with my foot and the area this morning has what appears to be a small indication of the algae reforming. I'm good with doing a SLAM but my question is - what the heck kind of algae grows in high chlorine levels? I've been monitoring my FC at lease every other day and for many weeks now it has never been below 6ppm and typically is over 8ppm. Last night, before I saw the algae, my measurement was 9ppm. I guess this could be pollen or dirt, but it was pretty green. Note, my CYA is 60 so according to the CYA chart, my target is 4ppm. I leave my pump running 24/7 and the SWG on 30% and I measure in the heat of the day. I just don't see how I've ever been at a chlorine level that would allow algae to grow. Any ideas?
I’m having pretty much the exact same issue and have been. We left for vacation and I had an FC of 8 with cya at 60. The day we left, I added a pound of Cal-hypo (which should have raised FC to 12)and let the salt cell run. I had someone empty the skimmer and come by and skim the pool, but the robot never ran. When I got home I had a few scattered green algae spots and my FC was 10 and CYA was 60. I was expecting to find leaves in the bottom of the pool, but not algae. Fast forward a week and after a few heavy rains, my pool got cloudy and I’m slamming the pool right now. I don’t get how I can get algae with 60 CYA and never letting my FC go below 8. I had algae problems with this pool last year as well. I keep my levels where they should be FC higher in fact, so yeah I don’t get it. I’m considering regular use of polyquat 60 as part of my maintenance regime as I don’t know what else to do other then start monitoring phosphates.
 
Last edited:

setsailsoon

Gold Supporter
LifeTime Supporter
TFP Guide
Oct 25, 2015
4,226
Palm City/FL
Pool Size
12800
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
CircuPool RJ-30 Plus
What does it look like? Green, dark green, black? Does it smear to more of a green color? Can you post a photo? I've seen local development of small algae colonies when FC drops close to minimum for the CYA level and I believe this was always due to a low flow area, an area where scrubbing missed them, black algae or a combination of these 3.

I hope this helps.

Chris
 

Mdragger88

Bronze Supporter
Jun 1, 2018
2,994
Hernando, Ms
Pool Size
26000
Surface
Vinyl
Chlorine
Salt Water Generator
SWG Type
Intex Krystal Clear
Depending on the settings of the swg you may be having fc dips near minimum during the day from the sun burning off the fc as a cya of 60 doesn’t offer quite enough protection in the dog days of summer but when you test (maybe after the sun has set & the swg has had time to catch up) you’re above minimum. Random testing at different times of day can catch this. Before raising cya to fix the original issue a SLAM Process is in order since you say u have visible algae. An Overnight Chlorine Loss Test can help u confirm this.
 

pb4uswim

Well-known member
Jul 23, 2020
328
Michigan
Thanks. In my mind, I went right to SLAM. I’ll do the OCLT tonight.
What does it look like? Green, dark green, black? Does it smear to more of a green color? Can you post a photo? I've seen local development of small algae colonies when FC drops close to minimum for the CYA level and I believe this was always due to a low flow area, an area where scrubbing missed them, black algae or a combination of these 3.

I hope this helps.

Chris
I was thinking this too - I hadn’t brushed for a couple days and the area is in a low circulation area.

It looked green. Not a real dark green.
 

pb4uswim

Well-known member
Jul 23, 2020
328
Michigan
Update.

Newdude - no one was in the pool today and that other spot on the ledge is showing a very small indication that something is growing/accumulating there.

Its hot and not feeling well today so I’ll put off the OCLT until tomorrow. Hopefully I’ll be feeling better tomorrow and if so, I’ll take advantage of the cooler morning to do a thorough brushing and run the robot. Tonight, I’ll just kick up the SWG to make sure there’s plenty of chlorine in the water.
 
  • Like
Reactions: Newdude

Newdude

Gold Supporter
TFP Guide
Jun 16, 2019
10,892
NY
Your FC is (or will be) elevated. At worst you are freezing it in time. At best you are fighting a little now. It can wait. Feel better.
 
  • Like
Reactions: pb4uswim

Enjoying this content?

Support TFP with a donation.

Give Support

pb4uswim

Well-known member
Jul 23, 2020
328
Michigan
Update - I did not pass the OCLT. Chlorine dropped by 1 (from 10 to 9) over night.

Problem is that I am to short on FAS-DPD to do a SLAM effectively. Product has been ordered but isn’t expected to be here until tomorrow. So, going to keep the FC high until Sunday and then start my SLAM.

Alternatively, I could wing it. I have LC and could bring the pool up to SLAM level and just wing it by adding a 1/4 gal every couple hours throughout the day. I have enough FAS-DPD powder to do an OCLT tonight and maybe one day will be enough. I’ll make my decision in about an hour before the sun hits the pool.
 

pb4uswim

Well-known member
Jul 23, 2020
328
Michigan
But I have had some small patches of algae the last couple days. Maybe I should just shock it today by bringing up to SLAM level and letting it float back down. Today would be a good day to do this because we‘re not going to use the pool today.

Or, just turn my SWG on super chlorinate and see what that does.
 

Texas Splash

Mod Squad
TFP Expert
LifeTime Supporter
Jun 22, 2014
33,444
Texas, San Antonio/Marion, South-Central Area
Pool Size
17888
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
CircuPool RJ-45 Plus
No doubt that even if you seemed to pass an OCLT, if you visibly see algae, you must SLAM. I wouldn't even bother with an OCLT until the water is crystal clear and there is no visible algae. Good luck!
 

pb4uswim

Well-known member
Jul 23, 2020
328
Michigan
No doubt that even if you seemed to pass an OCLT, if you visibly see algae, you must SLAM. I wouldn't even bother with an OCLT until the water is crystal clear and there is no visible algae. Good luck!
Thanks. I think I’ll just run the SWG on super chlorinate today in order to get the chlorine level up and hold things steady. Then when I get my chemicals, I’ll SLAM. Probably Sunday or Monday.
 
  • Like
Reactions: Texas Splash

pb4uswim

Well-known member
Jul 23, 2020
328
Michigan
It still mystifies me how this happened. Of course I can’t be 100% positive, but I’m pretty sure my chlorine level never dropped below 8 and even more sure it didn’t drop below 4, which is the target for my cya of 60. Oh well. It happened and now I’ll just handle it with the SLAM.
 

Texas Splash

Mod Squad
TFP Expert
LifeTime Supporter
Jun 22, 2014
33,444
Texas, San Antonio/Marion, South-Central Area
Pool Size
17888
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
CircuPool RJ-45 Plus
It still mystifies me how this happened. Of course I can’t be 100% positive, but I’m pretty sure my chlorine level never dropped below 8 and even more sure it didn’t drop below 4, which is the target for my cya of 60. Oh well. It happened and now I’ll just handle it with the SLAM.
Certainly. When odd scenarios like this happen, we first assume the FC level fell too low, but water circulation can also influence good chlorination. A small amount of algae can sit somewhere tucked away and not really impact the pool for a while then all of a sudden it gains strength and causes havoc. All you can do is increase to SLAM level and inspect/clean really well in all potential places of the pool. If you haven't done so already, make sure your reagents are fresh so that you are taking action based on accurate test results.
 
  • Like
Reactions: pb4uswim

Newdude

Gold Supporter
TFP Guide
Jun 16, 2019
10,892
NY
It still mystifies me how this happened. Of course I can’t be 100% positive, but I’m pretty sure my chlorine level never dropped below 8 and even more sure it didn’t drop below 4, which is the target for my cya of 60. Oh well. It happened and now I’ll just handle it with the SLAM
Yeah, weird for sure. Last time you may have not been paying as close attention beforehand, but I’m SURE after all you went through you have been on top of it since. 🤷‍♂️

Also, switch to 5ml samples until the kit comes. Each drop is 1 FC. Either at your current maintenance level or SLAM, the lesser accuracy won’t really matter for you.
 
  • Like
Reactions: pb4uswim

pb4uswim

Well-known member
Jul 23, 2020
328
Michigan
Yeah, weird for sure. Last time you may have not been paying as close attention beforehand, but I’m SURE after all you went through you have been on top of it since. 🤷‍♂️

Also, switch to 5ml samples until the kit comes. Each drop is 1 FC. Either at your current maintenance level or SLAM, the lesser accuracy won’t really matter for you.
We have storms rolling through the next couple days so I’ll just throw a bunch of chlorine in there, keep the pump running and deal with it in a couple days. My supplies will be here by then and the weather will be more cooperative. I’ll basically shock it for a couple days so I might be good after a day of SLAM.
 

pb4uswim

Well-known member
Jul 23, 2020
328
Michigan
So, got my reload on the chemicals and will start the SLAM tomorrow. Definitely have algae which is still curious to me.

Question - what is in the bottom of my pool? Is that dead algae that just accumulates in various places where there’s poor circulation? Or, is that live algae, which of course with my chlorine so high seems unbelievable. I’m trying to understand. It seems like I have an algae problem that the chlorine is keeping in check, but there’s not enough chlorine to clear it. Is that what’s going on?
 

Enjoying this content?

Support TFP with a donation.

Give Support