Brown sand like algae on bottom?

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S

skifffisher

Member
Feb 25, 2021
22
Alabama
Pool Size
21000
Surface
Vinyl
Chlorine
Salt Water Generator
SWG Type
CircuPool Universal40
Hello, I opened up our pool about 3 weeks ago- it's cleaned up and clear. I'm having a sand like extremely light weight algae form on the bottom, if I vacuum it with a (pool master fine filter)- which is a self contained vacuum, it's gone but back by the evening hours.
When I opened the pool I put some copper strike out in it, shocked it, vacuumed, brushed.
Last night I added 2 gallons of liquid chlorine as the pool chemistry was- Free chlorine 0.7 Total Chlorine 0.7. Ph 6.9. Alkalinity 85. Calcium 121
Cyanuric acid 69. Iron 0. Copper 0.4. Phosphate 0. Salt 3056.
Plan on adding 3lbs of soda ash today for Ph and slightly more calcium.
This is a 30' semi above ground pool saltwater. I can't seem to upload a picture.
Thank you very much for any help!
 
skifffisher said:
Hello, I opened up our pool about 3 weeks ago- it's cleaned up and clear. I'm having a sand like extremely light weight algae form on the bottom, if I vacuum it with a (pool master fine filter)- which is a self contained vacuum, it's gone but back by the evening hours.
When I opened the pool I put some copper strike out in it, shocked it, vacuumed, brushed.
Last night I added 2 gallons of liquid chlorine as the pool chemistry was- Free chlorine 0.7 Total Chlorine 0.7. Ph 6.9. Alkalinity 85. Calcium 121
Cyanuric acid 69. Iron 0. Copper 0.4. Phosphate 0. Salt 3056.
Plan on adding 3lbs of soda ash today for Ph and slightly more calcium.
This is a 30' semi above ground pool saltwater. I can't seem to upload a picture.
Thank you very much for any help!
Click to expand...
Sorry forgot to mention this morning I measured chlorine level with a DPD powder and it is around 6.
 
Is it sand or algae? If you don't have a sand filter, that rules that out. Also, how are you testing? Those look like pool store numbers and if so, they are wildly inaccurate and unreliable. You should get your own test kit and track it if you aren't.

If you FC has continuously fallen below 3, then it could be algae. Is your SWG turned on? If so, it should be generating more FC than that.
 
V___25 said:
Is it sand or algae? If you don't have a sand filter, that rules that out. Also, how are you testing? Those look like pool store numbers and if so, they are wildly inaccurate and unreliable. You should get your own test kit and track it if you aren't.

If you FC has continuously fallen below 3, then it could be algae. Is your SWG turned on? If so, it should be generating more FC than that.
Click to expand...
It's algae, sorry- yes I have a Cartridge filter. I have my own Taylor full test kit as recommended by this site. Used it all last year no issues. Was having trouble getting chlorine up so took to the store to make sure numbers were right. Generator has been on, showing it's pulling proper voltage and amps. However, it's not even maintaining chlorine levels so I'm suspecting the cell is not producing. This is my first time reopening a pool as I previously lived in FL with an in ground which stayed open all year.
 
mknauss said:
When you can, post a full set of test results.
Test Results

FC
CC
pH
TA
CH
CYA
Click to expand...
Thank you for reviewing this- did the test late last night after work- pool is now crystal clear after shock 2 days ago, brown very fine substance still scattered throughout the bottom (possible dead mustard algae?).
Results are;
FC 2
CC 0.5 (used the 10 ml mark for 0.5/drop results)
pH 7.4 (added 2 lbs soda ash two days ago)
TA 90
CH 140
CYA- I've apparently misplaced the small bottle 7/14 ml one so ordered a new one last night. A little 6 way strip shows 50-100 (I know these aren't accurate but wanted an idea).
Salt-went by generator which reads 3800 ppm.

Thank you!!
 

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Add 5 ppm FC worth of liquid chlorine each day until you can test your CYA level.

If you have the reagent, just use any vial to mix. 1:1 pool water and reagent.
 
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I had a similar thing happen a few weeks ago, despite testing regularly with TFP Pro kit and all numbers being in spec (and always keeping chlorine at the top end of the specified range). This is my first spring with my pool.

Here in TX, I think we were just having so many leaves, pollen pods, and bugs get in the water so frequently, that despite skimming multiple times a day, the overall organic content was rising until one day it won the battle vs my increasing chlorine additions.

Bottom line: I SLAMMED for the first time ever, added some DE to my sand filter, ran the filter round the clock, ran the robot while also brushing multiple times a day. In 24 hours, there was a reduction in the green/brown sand-like material, even though the water was a green-brown haze. Day 2-3, the brushing produced less poof and the water went to a whitish haze. By day 3-4 my OCL was zero, brushing produced no poof, but the water was cloudy and I had a party coming up so I maintained slam while filtering, backwashing, adding new DE, and brushing. By day 5-6, the pool was pristine. A week later, back to normal FC levels (always keeping it at the top end of the range)... brushing produces zero poof of any kind.

Moral of the story: now I know the poof that I was seeing wasn't sand or dust blowing in the pool, but the very beginnings of algae. In the spring, I won't hesitate to slam preemptively at the first sign that nature wants to wage an organic war with my pool.

Overall, the slam was a straightforward process that played out just like the videos and articles said.
 
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