Congrats on passing your OCLT
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In regards to your above statement of : "The next time it happens, and I'm sure it will," How about we see if we can prevent this from occurring again ever
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Here's some tips to preventing this in the future: Check your chlorine levels daily, and Always maintain your chlorine levels above the minimum for your current CYA level, if you never let it fall below the minimum for your CYA level algae won't grow.
Keep debris from sitting in the pool for any extended period of time, if a big storm blows a bunch of leaves, etc., in then use your leaf rake to get the debris out as soon as possible.
Brush daily, and vacuum as needed.
Increase your FC level slightly higher than Target especially after rain, on especially hot and sunny days, when you have large bather loads that have been swimming in the pool, etc. (I personally run my chlorine levels at 1-2ppm above the Target for my current CYA at all times for added protection, and to try to ensure I don't ever drop below the minimum for my current CYA.)
As you know the CYA test is somewhat a subjective test that can be off by +/-10ppm.
If you look at the Chlorine/CYA chart
http://www.troublefreepool.com/content/128-chlorine-cya-chart-slam-shock at the minimum ranges, if you read your CYA at 50ppm, yet it is actually 60ppm, then if your chlorine level drops to 4ppm which is the minimum for the 50 CYA that you thought it was, then that is going to be below the minimum of 5ppm for the 60 CYA that it actually is, so algae can grow. So that's exactly why I run mine 1-2ppm higher than the Target to give me a little more piece of mind, a little added insurance, and prevent that below minimum drop in case I made an error in reading the CYA results.
We want to see you back around here, But not because you are battling algae. I hope this helps, and have a wonderful day.