Possibly algae - CYA disappearing?

[Sdhb]

Hi,

I am noticing what I thought was sand but worry is potentially tiny blobs of algae on the bottom of the pool over the last days and weeks. I would brush it or robot vacuum and it would seem to return in the same areas. No CC readings really ever, but I'm reading that is not necessarily indication that I don't have algae. Decided to SLAM. Preslam readings are:

FC 8.0
CC 0
Ph 7.9
TA 75
CH 225
CYA 70
BOR 36
Temp 69
Salt 3800
TDS 4250 ( - this one from electronic device I have)

I lowered PH down to about 7.5 prior to slamming. Didn't confirm that with a test but added enough MA and assumed. Slam is 28PPM so I added what eventually became about 18L of Walmart (6%?) bleach just to get up to 27. Seems the Bleach is weak as I am consistently adding more than what is being suggested and still falling short (date code shows a month old only..) I've been holding more or less around 25-26PPM with Super chlorinate on and adding Bleach consistently just to keep it there. Still zero CC's so I assume FC is evaporating off rather than burning through contaminates...

OCCT loss was 1.0 last night, but I still see what I assume is algae popping up on the bottom (see attached).

Still FC seems to be burning off very quickly during the day so I tested CYA and suddenly CYA is 50. I don't understand how I could have lost 20 CYA in two days with no backwashing? I'm using DE in my sand filter and Borates this year for the first time. Also a liquid solar cover but that was in use last year as well.

I feel like there might be some kind of strange interaction happening. Also, surface of the pool seems just a bit glassy or oily the last few weeks. It's actually sort of pretty so I assumed maybe this is related to the Borates or the Liquid Solar cover that sits "on top".. possibly not related to my issue but just throwing out everything I can think of. We've had a couple rodent deaths in the pool the last few weeks but dealt with quickly and again, no CC.

Any ideas what happened to my CYA or what the deal is with algae (if it's algae? )..Do I just keep trying to SLAM for a while to see if it goes away?

 

[Texas Splash]

Good morning! Hard to tell what that stuff is at the bottom of the pool, but you are probably right to go into the SLAM Process. At Walmart, go to their outdoor section and look for their "Pool Essentials" liquid pool chlorine. It's 10% strength as opposed to the weak laundry bleach.

As for the CYA, might just a be a coincidence or testing variance. Before adding anymore stabilizer (after passing the SLAM of course), I would test the CYA again today or tomorrow if the sunlight is cooperating in your area. Do the test with a friend of family member. Each of you pour the solution into the tube but keep your results secret until the end and compare results. Each of you do a test and repeat it 2-3 times if needed before sharing results. If the average truly is 50, then just maintain the SLAM FC of 20 and press on.

When was the last time you opened the filter and inspected the sand or did a deep clean?

 

[Sdhb]

Thanks very much. Great suggestions. I did see the pool choline but pool math informed me that the price was better on the weaker stuff, adjusting for % factors so I cheaped out! This is my third season and I've never opened the sand filter. Hard to say if it has ever been done before then.

I passed the OCLT this morning again and no visible "algae" so I think my slam is done. I also added a skimmer sock to the underside of my skimmer basket..

Reading on here some more I'm also wondering if the substance could be pollen that keeps getting passed through the filter.

 

[Texas Splash]

I also added a skimmer sock to the underside of my skimmer basket..

Just to confirm, the sock is INSIDE the skimmer basket correct? It lays inside from the top to the bottom. When you said underside, I just want to make sure you don't have it wrapped on the outside-bottom to where it could get sucked off and into the pump.

 

[Sdhb]

Just to confirm, the sock is INSIDE the skimmer basket correct? It lays inside from the top to the bottom. When you said underside, I just want to make sure you don't have it wrapped on the outside-bottom to where it could get sucked off and into the pump.

I actually do have It wrapped outside, but it seems snug enough that it won't get sucked in. I have a skimmer angel type handle on my basket which is great for everyday use, but doesn't seem to work with skimmer socks.

 

[Texas Splash]

I actually do have It wrapped outside, but it seems snug enough that it won't get sucked in.

Yikes. You better pull that off. The socks tend to stretch and before you know it it's stuck somewhere in your suction line or blocking flow in the pump pot. I understand the issue with the Angel handle device. You might see if you can cut a very tiny slit or hole in the sock to allow it to slip over the handle so it can lay in the skimmer basket. It needs to be inside though.

 

[Sdhb]

Yikes. You better pull that off. The socks tend to stretch and before you know it it's stuck somewhere in your suction line or blocking flow in the pump pot. I understand the issue with the Angel handle device. You might see if you can cut a very tiny slit or hole in the sock to allow it to slip over the handle so it can lay in the skimmer basket. It needs to be inside though.

Probably sound advice. I feel like its' on super tight though, like a battle of epic porpotions just to wrestle it on. Wondering if I have smaller socks or pump just isn't pulling that much. Let me try your cutting idea.. Thanks for the advice, both primary issue and this new discovery!