14 days into Slam battling sand colored Algae - help


Sep 12, 2018
Helena, AL
I have been battling a sand colored algae for 14 days. Water is crystal clear, but there is stuff floating on top of the water it looks like a peeled sun burn skin floating on top. I am 14 days into slam and brush the pool daily and test a few times a day. Cannot pass OCLT. the PSI on the filter has been a little eratic so I backwash and rinse every time it gets above 20% normal operating PSI.
I was originally using 10% liquid chlorine to slam, 18 gallons over first 13 days then ran low so ordered 55 gallon 12.5% and have been using that for a day. My CYA Started at 40 and is now down to 30 because of all the backwashing. I have been testing at least twice a day, morning and night so perhaps I could be losing FCduring day but it has consistently been above 20 FC.

below is my full test today and it will be followed by tests over the two weeks.

I brush the pool every day and run the kreepy crawly for 5-8 hours most days
FC 21
PSI 10 (normal clean operating level)
cya 30
ch 75
ta 80
salt 2000
PH was 7.5 when I started the slam

4/24 FC 23 left
4/23 FC 24.5 7:30 am, psi 13, fc 21 8 pm, fc 23.5 10 pm
4/22 fc 26 psi 13 7 am, FC 22.5 3:30 pm psi 11, fc 25.5 psi 12.5 10 pm,
4/21 fc 26 7 am, fc 21 2 pm, fc 29 11 pm psi 12
4/20 fc 23.5 7:30 am, fc 21.5 9:15 pm, fc 24.5 11:15 pm
4/19 fc 22.5 10 am, fc 27.5 11 pm
4/18 fc 26 11am, fc 25.5 8 pm
4/17 fc 20 7 am psi 14,
opened pool on 4/3 and it looked like sand in the bottom, it was algae.... FC 7.5 when I opened, CC .5 water temp was 68 degrees

i also have a slimmer sock on my one skimmer and clean it at least twice every day, have been running pump 24/7 except when I am clean skimmer, back washing etc... please Help.

Texas Splash

Mod Squad
TFP Expert
LifeTime Supporter
With an inground, do you have a light? The kind with a hole/niche behind it? If so, have you pulled the light to clean behind there? Power off to the bulb and leave the light on the deck for a couple days? Also, when is the last time you opened the filter and did a deep clean of the sand? If not in a while, I would do that for sure.

Lastly, with a CYA of only 30, there's no need to have the FC so high. An FC of 12 is adequate. Hope this helps.


Well-known member
Mar 25, 2019
Houston, TX
Only sun and organic material will consume FC so you have something lurking in there if you cant pass OCLT. Keep SLAMing and make sure you have checked all the dark corners like light niche, skimmers, water features etc. Established algae has a film that will repel the chlorine and needs to be brushed to go away. Are you testing CC? How confident are you on your CYA testing?
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