Hi I just inherited a pool. It’s salt water. The entire pool is clear with the exception of some small black algae spots. Waiting on my test kit to come in the mail so I don’t have any info yet. Any suggestions? The vacuum doesn’t seem to get them. I scrubbed them but a day latter they were back.
Noobie with black algae spots
- Thread starter jahrens32
- Start date
- May 3, 2014
- 58,728
- Pool Size
- 6000
- Surface
- Fiberglass
- Chlorine
- Salt Water Generator
- SWG Type
- Pentair Intellichlor IC-40
Welcome to the forum!
Read Black Algae
I suggest you read through Pool Care Basics - Trouble Free Pool and even look at a few of our videos TFP-TV - Trouble Free Pool
Read Black Algae
I suggest you read through Pool Care Basics - Trouble Free Pool and even look at a few of our videos TFP-TV - Trouble Free Pool
Thank you. I’ve been reading through the black algae write up. It says that black algae is almost impossible in a vinyl pool but it meets all the other descriptions. I will follow those steps and see what happens.
Ok so I just got my TF-100 Pro test kit here were my levels:
FC: 0
TA: 100
CYA: 0
PH.: 8.2
CH: 375
Based on pool math app the recommended levels are
FC: 1-3
TA: 50-90
CYA: 60-90
PH: 7.2-8
CH: 0-650
I’m guessing I need to do a SLAM. That should kill the algae and get my levels to where they should be? The water is clear and no other issues besides the black algae spots.
FC: 0
TA: 100
CYA: 0
PH.: 8.2
CH: 375
Based on pool math app the recommended levels are
FC: 1-3
TA: 50-90
CYA: 60-90
PH: 7.2-8
CH: 0-650
I’m guessing I need to do a SLAM. That should kill the algae and get my levels to where they should be? The water is clear and no other issues besides the black algae spots.
So you need to do the following:
Lower the ph to 7.2
Add CYA to a level of 30 per poolmath
And do a OCLT to see if you do have a chemistry problem OR start a slam.
Lower the ph to 7.2
Add CYA to a level of 30 per poolmath
And do a OCLT to see if you do have a chemistry problem OR start a slam.
Ok got the PH down to 7.5 and CYA at 30. Raised the FC to 5.0 using liquid chlorine. Doing an OCLT tonight to see if I have an algae problem. I’m hoping I can just get the pool to proper levels and that will kill the black algae. I bought more chlorine in case I have to SLAM.
OCLT passed it stayed at 5. Now should I slam to kill the blah algae or bring everything up to normal levels and see if that works.
- May 3, 2014
- 58,728
- Pool Size
- 6000
- Surface
- Fiberglass
- Chlorine
- Salt Water Generator
- SWG Type
- Pentair Intellichlor IC-40
- Jul 17, 2019
- 3,730
- Pool Size
- 13000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Pentair Intellichlor IC-40
The recommended FC level you posted is way too low. Even if you keep your CYA down at 30, your target should be 4-6.
After you get rid of the algae (or at least confirm you do not have algae) I would get your CYA up to recommended levels and follow the Salt Water Generator version of the Chlorine/CYA chart. See my signature if you need the link.
Lastly, you posted that your FC was 0 and you have a salt water pool. Is the SWCG turned on and working correctly?
Thanks for the help. I re-read that article. I am planning to keep the CYA at 30 so that I can raise the FC to between the top of the recommended range (6) and the slam level (12). Hopefully this should kill the BA along with the other steps in that article, without having to do a full SLAM.
Yeah, that was a typo in my last post. You are correct. As far as the SWG goes, I don't know much about these. I am still researching on this site. All the lights are green though so I assume it is working. After the 0 FC test I tested again first thing in the morning and the FC came up to 1, not sure what the SWG would produce by itself. The OCLT passed last night so we shall see if it keeps up.
- Jul 17, 2019
- 3,730
- Pool Size
- 13000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Pentair Intellichlor IC-40
Ok cool, green lights are good. Your SWG is a bit undersized for your pool, but an IC15 in a 15K gallon pool running 24/7 @ 100% will produce 4.8 of FC per day.
Did you have the SWG off when you did the OCLT?
No I forgot that stop. Guess I'll do another one today. haha. It is currently running 24/7 at 50%. I am in the process of replacing the timer. Maybe I need to run it at a higher percent?
- Jun 22, 2014
- 47,969
- Pool Size
- 17888
- Surface
- Fiberglass
- Chlorine
- Salt Water Generator
- SWG Type
- CircuPool RJ-45 Plus
Time will tell. For now, keep some liquid chlorine handy and be sure the FC remains somewhere in that 5-7 range today. Report back with the results of your second Overnight Chlorine Loss Test. That will drive what to do next. Don't forget to turn off the SWG tonight.
No I forgot that stop. Guess I'll do another one today. haha.
OK, so I did a proper OCLT. FC went from 4.5-3.5. So I guess that’s barely a pass.Time will tell. For now, keep some liquid chlorine handy and be sure the FC remains somewhere in that 5-7 range today. Report back with the results of your second Overnight Chlorine Loss Test. That will drive what to do next. Don't forget to turn off the SWG tonight.
What surprises me is that I had the FC 10.0 at 1:30 pm and by 8:30pm it was down to 4.5. I tested the CYA and it was below 30. I’d say about 20 but the sight gauge is hard to tell anything below 30.
My plan next is to add some more CYA and try and get it to a true thirty reading and then keep the FC around 9.0 for a couple days to kill the rest of the algae. It does seem like it is dying.
My second option would be just to get all levels back to the recommended range. Any thoughts?
OK, so I did a proper OCLT. FC went from 4.5-3.5. So I guess that’s barely a pass.Time will tell. For now, keep some liquid chlorine handy and be sure the FC remains somewhere in that 5-7 range today. Report back with the results of your second Overnight Chlorine Loss Test. That will drive what to do next. Don't forget to turn off the SWG tonight.
What surprises me is that I had the FC 10.0 at 1:30 pm and by 8:30pm it was down to 4.5. I tested the CYA and it was below 30. I’d say about 20 but the sight gauge is hard to tell anything below 30.
My plan next is to add some more CYA and try and get it to a true thirty reading and then keep the FC around 9.0 for a couple days to kill the rest of the algae. It does seem like it is dying.
My second option would be just to get all levels back to the recommended range. Any thoughts?