Started a SLAM

[dariushd]

Ok after an RO I started a SLAM. Cya at 30, ph at 7.6. I got the FC to 13 around 5pm, added more at 9:30pm to get it back to 13. But over night it went down to 9.5 when I checked at 6:30am. I got it back up to 13, of course but two questions:
1. Is it ok that it dropped below the FC goal for a SLAM for several hours?
2. Since this was overnight and no sun, does a drop of 3.5 confirm I have an algae issue?

I have almost no CC, and the water is crystal clear. From what I've learned here, that 3.5 FC drop does confirm algae (that keeps showing up on my shaded pool wall!). How long do you think the SLAM will go?

Lastly, testing cya on a cloudy day gives you a false read, right? As it's not nearly as bright and the dot disappears sooner? I'd been getting 30 yesterday with a sunny day and now 40 early morning overcast. I also noticed that the Taylor cya test skewed a bit higher than the Blue Devil kit that has a larger comparison tube. Which should I listen to?

 

[spinPHD]

1. It's ok that it dropped, but the longer you can keep it at SLAM level the faster SLAM is. However, you can't add anything at night anyway while you're doing an OCLT.
2 3.5 does confirm you need to SLAM. At 9:30, did you test to confirm that your FC got back up to 12 or did you just add chlorine and assume it reached its target? Reason I'm asking, is you need to confirm your FC level to make sure OCLT is accurate.

Go with the sunny CYA reading. Unless you added stabilizer or had large water replacement, your CYA won't change day to day. Trust the Taylor kit

 

[dariushd]

I tested about an hour after I added chlorine last night, doing the 10ml version of the test (like every other time).
I have not added conditioner, but since the RO competed late yesterday, I thought I'd let the pool settle for a few days and seeing if anything fluctuates. Taylor has me at about 35, Blue Devil at 30. ill test cya one last one when the sun comes out. I'm just giddy I'm not at 250 anymore.

 

[spinPHD]

If you're getting 35, you want to round up and chlorinate at the 40 CYA level