Algae with Chlorine

Miniduper

Member
Apr 19, 2020
19
Las vegas
I've been closely monitoring my pool everyday and testing chlorine morning and night. FC has always been between 6 and 10 FC. I left my solar cover on these past couple days and today when I took it off the cover the pool was cloudy and green. Am I missing something? How is it possible for algae to grow with that much chlorine? Thanks
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
36,977
Laughlin, NV
Pool Size
6000
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
The FC is dropping below minimum somewhere in the system. When you have the cover on, do you still run the pump some each day?
 
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Dirk

Gold Supporter
TFP Guide
Nov 12, 2017
8,624
Central California
Pool Size
12300
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
How were you storing your cover? Was it wet and rolled up for a period of time? You might have grown yourself a little algae outbreak on the cover and then planted it in your pool! And then it overwhelmed what chlorine was in there, and then took off.
 

Miniduper

Member
Apr 19, 2020
19
Las vegas
With the cover on I was still running the filter and swg 5 hours every night. Since the solar cover isn't really a sealed cover it just floats on top of the water and there were tons of leaves and debries trapped at the bottom of the pool for days. I figured I could clean those out this weekend. Can having things like that in the pool regardless of FC level cause issues? As for the cover it was sitting in my rocks baking in the Las Vegas heat so probably no algae from there. Crazy to think with a FC that high that algae could bust out. I'm really leaning towards the problem being poor circulation in some way.
 
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mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
36,977
Laughlin, NV
Pool Size
6000
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
Hard to say. Those little pools with tiny pumps are not known for their circulation. So when you stop swimming in them, mixing suffers. Only way algae can start is for the FC to fall below minimum somewhere in the system.
 

Dirk

Gold Supporter
TFP Guide
Nov 12, 2017
8,624
Central California
Pool Size
12300
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
Can having things like that in the pool regardless of FC level cause issues?
Chlorine goes to work on anything organic: algae, sweat, pee, bugs and certainly leaves, to name a few. That's not to say it isn't possible to keep FC up with leaves in the pool, but the leaves would definitely deplete it. You might have had a perfect storm of a little extra heat, not enough circulation, just the right amount of light, a little light on FC and one too many leaves. Could have been the last jug of chorine was a dud (old or weak) and you thought you dosed to 6 but it never got that high. Whatever. Just enough factors combined to drop your FC below your "algae threshold" and then it took hold, dropping FC even further. Like a snowball effect.

So you SLAM and when done you up your FC a point or two. Stay closer to 10 than 6. As now you know what level is not quite enough for foolproof algae protection. I had that happen to me just this summer. Few unusual factors combined and dropped my FC below my algae threshold and boom. Now I know where it is.
 
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