How to stop little algae spots?

[Scottamus]

Hi, I started using the Taylor test kits and this site exclusively in March 2024, and it’s been going great! I have this weird issue lately where all my chemicals seem consistently fine, but maybe every 1-2 weeks, I get like 5-7 little dime-sized dots of like green algae on the bottom. I’m attaching a picture to show you. They brush off pretty easily, but I keep getting more. Not a lot, but some.

My chlorine levels stay around 7-8ppm, and I keep all my chemicals in range and test regularly…they don’t seem to spread, but I wonder what they are and how I stop it.

Maybe a month ago my chlorine got real low and we had family about to come stay with us, so I didn’t want to slam it fully, but I did like a mini slam, where I got the levels up at like 12-14 for a few days, until my combined chlorine got back to normal (it was at 1.0 for a while and then back to <= 0.5 and chlorine stabilized again.

I did slam it fully probably 4-5 months ago.

Any ideas??

 

[Scottamus]

I should also mention that I’m adding salt - it was at 2800 last week but with the rain it’s down to 2600, which is new.

 

[Newdude]

Overnight Chlorine Loss Test to see if anything is brewing. It may be environmental, or it may be algae.

 

[Scottamus]

Ok, still 6.0 at 9:36pm. Will test before sunrise.

 

[Scottamus]

Dang, yep. Down to 5.0 just before sunrise. Ok thanks!

 

[sande005]

It appears that determining CYA is giving you a bit of difficulty. If you are between lines, round up to the next. So if you think it is between lines at 85, call it 90.
Over the last couple of months, it seems like your CYA was 75 (80), then a reading would make it appear to drop to 50 so based on that test, you added CYA. Then repeat a bit later.
By your logs, you were at 80 a couple of months ago, and then added 70 oz (total) of stabilizer at 3 different times. That should have pushed you up to 130-140.
Unless you have done a LOT of water replacement, something in your testing is way off. Water replacement is the only way CYA can drop in such a short time.
Dilute the next batch of water for the CYA test 50% with tap water first, and test again. If near 80, it will show as 40. If it is really a lot higher, it will show as 1/2 (so 140 would be 70), etc.
I'm guessing you are off the charts high in CYA, and therefore comparatively super low on the amount of Cl that would be needed. If such is the case, you'll need to replace a lot of your water.
Given the bouncing of your test results, do the test a couple of different times during a day, to zero in on your actual amount. Lighting conditions, changes in how you view the tube, etc. may be skewing your readings for this notoriously more subjective test. Here's how to test in detail: CYA Testing - Further Reading

 

[sande005]

And...once you get your CYA in hand, then it will be SLAM time to get rid of that algae. If your CYA is really high, it will be close to impossible to dump as much Cl as might be needed to do a SLAM.

 

[Scottamus]

Hi,

Thanks! Interesting that you can see my logs…cool. I need to learn how to see my own lol. I live in Tampa Florida, and we have had an epic rainy season. We’ve had several afternoon storms dump 4.5”-5.5” in like 90 minutes. And regular storms most other days. So I have had a LOT of water displacement. Draining the pool 1-2 times a week all summer. Sometimes more. Depending on where you look, we are like 16”-18” over the annual rainfall average already, with over three months to go! Lol. I wondered if I should round up or just put it at say, 85. I guess rounding is the approved method. But yes, those times I had to add a bunch were after huge rains where I had to drain like 5-6” off, sometimes more than once in between.

 

[sande005]

The log magic is via the Pool Setup section in Pool Math, where you can link it to your user name here. Just hover over any user name in a post header, and if turned on, there is an option to bring up their logs. A big assist in helping others figure out what to do.
If there is a chance to again lower the pool very soon, and get the CYA down, that would help in doing a SLAM. Lower target for the FC. Or you might want to just shoot for a high normal amount of Cl (12 ppm) to keep things at bay, and see if that hurricane that is projected to aim at Mobile, AL has a side effect of dumping a lot on you toward the end of the week. Then move on to a real SLAM after.

I'm of the mind with a SWCG to always keep it toward the high side of the range when running normally. Gives a buffer if something happens that would make it otherwise drop too low.

 

[Scottamus]

Thanks for all the advice. My tests are all good today, but I did see a few little tiny dots of green. I’m going to do a full slam now.

 

[TinFoilHat]

Don't forget to brush the pool and those spots once your FC is at SLAM level to break the film of the algae.