Is this algae!?

PoolStored said:

Do you have a speedstir? If not, I'd get one. My brother owned a pool for 30 years. He and I did side by side FC testing. Him swirling and me with speed stir. We were 1FC different, him higher...swirling is not as effective and speed stir to get consistent results. I'm stretching here, but trying to find the answer.

Another thought. Are you holding the drop bottle vertical? If not, do so.
Drop the drops VERY slowly. Let them form and drop under their own weight. If you squeeze the drops out, they can be smaller than they should be. I'm just looking to remove any variability.

For your next OCLT, I want you to clean and dry your test vial with rubbing alcohol before each test. Make sure it dries.

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I got it! Not sure if the drain covers did it, or the extra few days of SLAM, but I measured 24.5ppm FC last night at 9pm (0.5ppm HIGHER than I expected to see based on my chlorine dosing at 7pm), and I measured 24ppm FC at 4:30am, or 0.5ppm OCLT.

I am still measuring 0.5ppm CC. I have never not read 0.5ppm CC. But my mixture never turns bright pink, it only turns that “ultra-faded one drop before you go perfectly clear” pink, so I’m unsure if that IS in fact a 0.5ppm CC reading, or if I should disregard the result because it doesn’t actually turn pink…

I have read in multiple different places on this website that you should either start a SLAM if you have 0.5ppm CC and that you should start a SLAM if you have over 0.5ppm CC. This is a bit confusing if you’re a noob…

And the graduations are already rubbing off on my TF FAS/DPD test vial. I believe they say to air dry it, and I have wiped it with a paper towel a couple of times in the 6 days I’ve owned it, so I guess I should stop that. Still, minor gripe. I do prefer Taylor’s graduations.

I will 100% be buying a speedstir! Hand swirling 49 drops of reagent while trying not to go cross-eyed is a Herculean task.

@PoolStored, I wanted to thank you for the hand-holding on this. We bought this house in September 2022, and the previous owners had freshly filled the pool for the listing (they said they hadn’t used it in years). It didn’t even sparkle then with fresh water like it does now. Last year I shocked it repeatedly, and it never came close. I guess I need to get out there and take a picture…