I have a 33000 gallon gunite pool. Earlier this year, I did a 3/4 refill. I corrected the PH and alkalinity with numerous gallons of acid. My CYA is 31 and the water itself is perfectly clear at this time. My issue is that there are several sections with algae on the walls and bottom. No amount of scrubbing with a metal brush will remove it. For this reason, I don't feel it is yellow algae. I have SLAMed the pool 3 different times with hours of scrubbing the affected areas to no avail. I have kept the CA well above the SLAM level for days on end. Again the water is perfectly clear but the walls never become algae free. Extremely frustrating. Any help would be appreciated.
Embedded algae
- Thread starter spete
- Start date
- Jun 22, 2014
- 47,855
- Pool Size
- 17888
- Surface
- Fiberglass
- Chlorine
- Salt Water Generator
- SWG Type
- CircuPool RJ-45 Plus
Welcome to TFP! 
We understand the situation, but our first step is to always see a full set of water test results from a reliable test kit - either a TF-100 or Taylor K-2006C. Much like an annual wellness exam by your doc who needs fasting labs first, reliable water testing tells us a LOT, even when your water appears to be clear. Do you have a TF-100 or Taylor K-2006C?
The proper test kit is required to successfully perform and complete the SLAM Process. Those who pass the Overnight Chlorine Loss Test but still see staining may just be dealing with organic staining. Depending on the severity and duration of the algae, some stains can take a long time to treat.
But I would also encourage you to post some pics of the staining as well. Pics, along with water test results, can tell us a lot.
We understand the situation, but our first step is to always see a full set of water test results from a reliable test kit - either a TF-100 or Taylor K-2006C. Much like an annual wellness exam by your doc who needs fasting labs first, reliable water testing tells us a LOT, even when your water appears to be clear. Do you have a TF-100 or Taylor K-2006C?The proper test kit is required to successfully perform and complete the SLAM Process. Those who pass the Overnight Chlorine Loss Test but still see staining may just be dealing with organic staining. Depending on the severity and duration of the algae, some stains can take a long time to treat.
But I would also encourage you to post some pics of the staining as well. Pics, along with water test results, can tell us a lot.
Maybe not the correct or best advice but worked for me as a last resort, when I had a hard time with black algae. I used a pressure washer. It got everything off the walls and floors. I used the large floor attachment for the floors and a wide spread attachment for the walls. If you do this, whatever u do do not use the finer spray attachments. The stream is to strong and can chip the plaster. Getting a pool company to acid wash is probably better but a way more expensive option. Regardless is worked for me and the black algae never returned. Good luck.
Thanks, Texas Splash. Actually, I joined TFP in 2016; not sure why I was indicated as a new member - maybe because this is my first thread. I am very familiar with the SLAM method and have used it successfully for many years, but this year is different. This algae will not scrub off.Welcome to TFP!
The proper test kit is required to successfully perform and complete the SLAM Process. Those who pass the Overnight Chlorine Loss Test but still see staining may just be dealing with organic staining. Depending on the severity and duration of the algae, some stains can take a long time to treat.
But I would also encourage you to post some pics of the staining as well. Pics, along with water test results, can tell us a lot.
FC - 8.1 (on the way down from SLAM)
TC - 8.3
PH - 7.5
CYA- 31
TA - 136
CH- 169
Because I did a major refill on a large pool, my TA was high but getting close to normal - I have added 6 gallons of muriatic acid in the past weeks.
I'll see if I can post photos but I doubt they will show the visible embedded area.
Thanks. I do think your method would work but because I did a refill this year, I am reluctant to empty it again. Hopefully I can resolve this another way.
- Jun 22, 2014
- 47,855
- Pool Size
- 17888
- Surface
- Fiberglass
- Chlorine
- Salt Water Generator
- SWG Type
- CircuPool RJ-45 Plus
Yes, that caught me off guard.
Say, which test kit are you using? The numbers seem a bit odd to us. 
No. I didn't empty the pool. I used the pressure washer with the pool filled. I got in the pool and used it. I have an extra long hose and it's not like the gun or anything will be damaged it's meant for water. I've actually done this method 2 or 3 times and have had no issues. Saved me alot of headache. I continued slamming after that to make sure everything was dead.
Now that is very tempting. Since I've had no results with metal brushing or keeping chlorine levels high, this makes sense. My water is still quite cold but I will reach as far as I can to test it out. Thanks! BTW, I don't have a floor attachment. I was going to try using the wand on the widest setting and gently applying at some distance from the wall to avoid damage. Thoughts?