Need some help with algae in my pool

jorge18

Well-known member
May 2, 2018
201
Miami, Fl
So I've been battling this algae for a little while now and I need some help on what to do. I've tried fighting it with chlorine but as you can see with my levels and pictures, it's not doing much. I've determined that it's mustard algae from my research but I'd like to know what would be the best way to fight it. The algae brushes away pretty easily but keeps coming back.

Just tested the following:

PH- 7.5
FC- 15
TA- 90
CH- 375
CYA- 90

Pictures of the algae:






Let me know what you think and what I should use.

Thank you!
 

JJ_Tex

Gold Supporter
Bronze Supporter
Jul 17, 2019
2,524
Prosper, TX (DFW)
Pool Size
13000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
The best way is still chlorine, but you need a lot more.

With a CYA of 90, you need to get your FC up to 35 which is SLAM level. Your 15 is just keeping it mostly at bay. Alternatively, you can lower your CYA by doing a water exchange so that you do not need as much FC to kill the algae. See the chart in my signature if you need.
 
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jorge18

Well-known member
May 2, 2018
201
Miami, Fl
I didn’t SLAM because I saw that my chlorine levels were so high that I figured it would be enough to kill everything in there (obviously not).

So the recommendation will be to go through the SLAM process and see if it goes away?

With the amount of rain we’ve been getting lately, getting the CYA down should be relatively easy.
 

Cwiggs

Gold Supporter
Aug 31, 2019
293
Phoenix, AZ
Pool Size
21000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
CircuPool RJ-60 Plus
So the recommendation will be to go through the SLAM process and see if it goes away?
I would start there. If you think it's mustard algae you'll want to follow the guide on that (I linked it above), however usually it's not mustard algae. I'd be curious to see what it looks like after you SLAM the pool.

The M in SLAM is maintain, so try to maintain the FC level as best as possible.
 

GerryB

New member
Jun 28, 2021
1
Niagara Region, Ontario
I thought I already posted an answer, but I’m new to the forum and it doesn’t seem to be there! I agree with the SLAM, but I found a product that works really, really well for our pool, which is a 32-year-old 18x36 rectangle with radius corners and fiberglass stairs. We used to have lots of problems with algae showing up on certain parts of the pool walls and the stairs. I found that using a 1-micron Slime Bag cloth filter on the pool’s first return outlet from our sand filter has kept our pool algae-free for years now, and we always have sparkling-clear water as well. I'm amazed at the amount of green that the bag can collect in one day! We buy a new bag every year when we open the pool. The filter bags wash easily with a hose, and one bag can be re-used all season. The bags are expensive, so I bought some 1-micron filter material online and started making my own. I use heavy-duty thread and size 18 needles, and my sewing machine handles the material with no problems. I can now get two home-made bags for less than the retail cost of one. Until we started using the filter bags, nothing else seemed to work.
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
43,662
Laughlin, NV
Pool Size
6000
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
I found that using a 1-micron Slime Bag cloth filter on the pool’s first return outlet from our sand filter has kept our pool algae-free
Filtering does not eradicate algae. It may filter out dead algae, but there is still live algae in the water. Chlorine eradicates algae.
 
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Victor Newman

Bronze Supporter
Sep 6, 2014
70
Grants Pass, OR
We might have yellow/mustard algae......but my question is: after getting water to SLAM, why do you brush the pool ? Is it to dislodge the algae and get to the underside....or does it have a hard shell that needs to be roughed up ? Or are there other reasons ? TIA
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
43,662
Laughlin, NV
Pool Size
6000
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
.but my question is: after getting water to SLAM, why do you brush the pool ? Is it to dislodge the algae and get to the underside....or does it have a hard shell that needs to be roughed up ?
Algae creates a biofilm to protect it. Brushing disrupts the biofilm and disperses the chlorine throughout the algal colony to kill it.
 
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