Pool Opening - Green with Issues

njwaves

Member
May 23, 2007
14
Central Jersey
Opened a very dark green pool this year. Probably had some unresolved issues at closing.

After adding algaecide (28oz of Poly 60) and chlorine (liquid from carboys), and vacuuming and brushing several times over the last few days, the shallow end is getting clear, but the deep end is still pretty dark. Any way to tell what kind of algae it is?

When vacuuming the debris the day after I put in the algaecide, it looked like it was just coming back into the pool through the return. I have a sand filter and had the sand replaced last year. I vacuumed to waste which I think helped, but I'm wondering if this indicates a problem with my filter? Also after running the filter for a while, I notice that debris seems to pile up under the stream of water from the return in the shallow end. Finally, after backwashing yesterday, it took a little while for the pump/filter to return to normal pressure and the water from the return to stop bubbling/surging. Any thoughts?

My pool: approx. 20,000 - 25,000 gal free form vinyl liner.

My chemicals: CYA was zero at opening, but I added about 4 lbs to my pool. Waiting for reagents from TFTestKits. I'm maintaining FC at 3 - 5. pH is about 7.4 - 7.6. TA is 70.

Thanks!
Jim
 

chem geek

TFP Expert
LifeTime Supporter
Mar 28, 2007
12,082
San Rafael, CA USA
If it's green, such as dark green or cloudy green, it's green algae. There are many different species, but they all work the same way in terms of normal shock levels to get rid of it. If it were a clear or light green, then it could be copper metal ions (or iron, if one has a blue pool surface), but that's not your situation.

The other two main types of algae are quite different. Yellow/mustard algae is more like a powder that is yellow/mustard in color and prefers shade and is more resistant to chlorine. Black algae is also quite different embedding into pool surfaces (especially plaster) being black and needing the head scraped off to expose deeper parts to shock levels of chlorine. Pink slime is actually a bacteria and is pink and slimy on surfaces just like it sounds. White water mold or tissue mold looks like tissue paper and breaks up easily (and is a fungus, not bacteria or algae).
 

njwaves

Member
May 23, 2007
14
Central Jersey
Yellow/Mustard algae is a possibility since I did notice a lighter green slightly yellow in the shallow end the day after adding the algaecide. Is the higher chlorine shock level + algaecide the way to go? Today is day 4. I added 1 bottle of algaecide 4 days ago and have maintained chlorine in the 3 - 6 range. I'm waiting on the CYA reagent, but starting at zero and adding 4lbs probably brings me to about 20. I plan to get more CYA today. Any recommendation on how much algaecide to add if any?
 

mkenyon2

Well-known member
Nov 25, 2009
236
Cleona, PA
I'm pretty sure I had green algae this spring. It was green on the pool cover, and got (accidentally) dumped in. At times tho, it looked yellowish. I shocked a couple days at Mustard Algae levels just to be safe, but as I saw the nightly FC drop getting lower, I went back to standard shock, and was still able to finish. Took me a week, and it wasn't a 'swamp' when I opened, so you might have a bit longer time to go.

I didn't use algaecide, but I did use some CalHypo. It was more expensive than shocking with bleach, but I used it for 2 reasons:
Easier to find and transport (buying 20 or so jugs of 6% bleach is a lot of work)
My CH (Calcium Hardness) was low enough
But I did start with bleach.
 

njwaves

Member
May 23, 2007
14
Central Jersey
Thanks for the good information. After reading a little more and seeing a picture of mustard algae, I think I have green algae, just a lot of it. Will continue to fight with shock levels of chlorine. Unfortunately chlorine dropped to 2 when I got home from work today. The weekend should make it easier to keep the levels high enough. To be continued...
 

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