What am I fighting?

[MLock]

If my FC gets eaten up during the day (maybe 7 in the morning and 0.5 by evening), but the pool has 0 or 0.5 CC in the evening... am I battling algae or the sun?

I guess what I'm asking is, if it were algae, wouldn't I see higher CC?


For instance, yesterday morning:

FC: 7
CC: 0
TA: 200
pH: 7.6
CYA: 50
Water temp: 89

Air temp yesterday was 94 degrees, lots of sun, pool was open (automatic cover) from 7a-12p and again from 5p-9p. At 9p:

FC: 0.5
CC: 0
TA: 200
pH: 7.6
CYA: 50
Water temp: 93

When I'm down to 0 or close to 0 on FC, the seams of my liner darken up. The water is consistently very clear.

My only guess is that I'm (still) fighting algae, which FC consumes, then more FC consumes the CC, and when I test, both are cancelled out. Is this off-base?

 

[RobbieH]

Perform the overnight chlorine loss test, post results.

 

[MLock]

Sure. Should have mentioned that. Two nights ago, I raised FC to 14 after the pool was out of the sun, and then the next morning (see results above) I was at 7.... but the CC was 0, which is what's confusing me. When I was battling the hardcore algae at open this year, my CC would be off the charts.

 

[Bama Rambler]

It's more common to have no CC's even with algae than it is to have them. Given that you lost 7 ppm FC overnight you need to start the shock process and keep it at shock level for your CYA until you pass the OCLT.

 

[MLock]

It's more common to have no CC's even with algae than it is to have them.

Awesome info. Definitely didn't know that and believed the opposite. Thanks!