Stuff that recurring comes back

[Grayman43]

Hi,
Ever time shock my pool this stuff comes back in exactly the same spots. It’s been going on a while so just vaccumed every day.
detail.
fC 9
ph 7.8
alk 80
cya 35
ch 200
sand in Filter replaced last year, I vacuum very slowly to get it up and within 20 minutes it shows up again. Interesting if I leave pump not running it does not come back.
thoughts? Here is a couple of pics.

 

[Bperry]

Hi,
Ever time shock my pool this stuff comes back in exactly the same spots. It’s been going on a while so just vaccumed every day.
detail.
fC 9
ph 7.8
alk 80
cya 35
ch 200
sand in Filter replaced last year, I vacuum very slowly to get it up and within 20 minutes it shows up again. Interesting if I leave pump not running it does not come back.
thoughts? Here is a couple of pics.

What’s the normal chlorine level you run at? Algae coming back seems to indicate too low. Just confirming those test results from your own test kit and not a pool store?

 

[Oly]

Why are you needing to "shock" your pool?
Confirm if you have an active algae population with an
Overnight Chlorine Loss Test. If you fail this test you need to complete the
SLAM Process. Once you control the algae you can backwash your sand filter to remove the dead debris or vacuum the debris out before it gets into your filter.

 

[Grayman43]

What’s the normal chlorine level you run at? Algae coming back seems to indicate too low. Just confirming those test results from your own test kit and not a pool store?

Test results are from Taylor 2006 kit. what puzzles me is I passed the ONCL but still have a bit of green alage. Got it all out and bottom was clear. I run my pool pump again and it’s back in the same spots. then I vacuumed again and it’s gone but back in same spots . When I don’t run the pump, it does not reappear.

 

[Grayman43]

Normal FC is about 4 to 5. I got here because I missed a week of putting chlorine in and got some alage. My main question is why is it coming back to the same spot? And is it dead algae from looking at the picture?

 

[Oly]

With active algae and your CYA of 40 you will need to increase your FC to the correct SLAM level and hold it there. With a recent algae outbreak the SLAM process should be over relatively quickly.

 

[Bperry]

Normal FC is about 4 to 5. I got here because I missed a week of putting chlorine in and got some alage. My main question is why is it coming back to the same spot? And is it dead algae from looking at the picture?

You’ll need to SLAM in that case.keeping FC that low is kinda dangerous in that if you lose 3ppm in daily consumption, you end up way below minimum pretty quick.

 

[Grayman43]

Ok thanks . could you tell anything from those pictures? Does it look like live alage or dead ? Will alage tend to come back in the same spots

 

[Toxophilite]

Ok thanks . could you tell anything from those pictures? Does it look like live alage or dead ? Will alage tend to come back in the same spots

Dead algae will fall out and settle where a current eddy allows. It's following your underwater circulation currents and that's probably the calmest area to settle out.