Light cloudy green in deep end - Small FC loss overnight


New member
Jun 14, 2010
Tewksbury, MA
FC = 4.5
CC = 0.5
pH = 7.6
TA = 80
CH = 40
CYA = 35

I recently purchased a house with a pool that had not been opened the previous season. It was almost black when I started but thanks to this site I have started on the right path. I ordered K-2006 and stocked up on 12.5% chlorine. Following Turn Green Swamp into Sparkling Oasis directions, I got the water almost clear. I first fished out as much leaves etc and then brought CYA up from 0 to 35. Adjusted the pH up to 7.2 and TA to 80. I shocked away (bringing the FC level up to about 13) and checking every half hour or so and bringing level back up when needed. At the end of the day the FC was at 14 and next morning it was 13. Doesn't this mean there should be no more algae?

I continued to keep pool at shock (between 10 - 14) throughout the next 2 days. The filter was always running and pool cleared to point where the shallow end looks great but the deep end has a cloudy green but you can clearly see the bottom. I continued to let filter run for a few more days and when no improvement showed I brought it up to shock level once more (did not maintain at shock though) and brushed all surfaces. This did not seem to make much of an improvement. If the algae was dead I was expecting to see cloudy gray. Two days ago my FC was at 6.5 at night and 6.5 in the morning. If algae was present wouldn't my FC levels be dropping more?

It has been 2 weeks since I first shocked the black pool. It has been in this green deep end state for the last week with not much improvement. Should I bring it up to shock level again or higher?

Bama Rambler

Mod Squad
TFP Expert
LifeTime Supporter
Jun 22, 2009
SouthWest Alabama
It sounds like you're not getting good circulation in the deep end. Is your main drain working correctly?

Try aiming the returns into the deep end.

If you truely passed the overnight loss test then you're done shocking, but it can take some time for the pool to clear.

I'd suggest trying a clarifier at this point and vacuuming up what falls to the bottom. You can vacuum to waste if you'd like.


LifeTime Supporter
Jul 29, 2009
I'd take your water to a pool store and have them test for metals... particularly copper.

You may need to get a sequesterant in there.
Thread starter Other Threads of Interest Forum Replies Date
R Just Getting Started 5
M Just Getting Started 3
A Testing and Balancing Your Water 14

Other Threads of Interest