My wife just called me at work and said she saw a bunch of algae in the pool. She brushed it, but I'm perplexed. I've suspected some algae over the last few weeks, but haven't been sure if it's dirt or algae. Having a blue/green pebble finish doesn't make it as easy to discern algae.
What has me perplexed is that FC has been 3.5 - 4.0 every time we've tested it (which is usually 3 times a week unless something seems wrong). When we've had algae problems in the past, they've been preceded by a sudden drop in FC. I've seen the pattern and know to go into shock mode. But that's not the pattern I'm seeing this time.
Thanks to TFP, I'm pretty successful at shocking the pool and getting things back in order. What I'm trying to figure out now is what's causing the algae when everything looks good?
I'm going from memory of my test on Saturday, but I believe these were the values on Saturday morning:
- Temp 74 F (this is early in the morning; it will get to the high 70s in the afternoon)[/*:m:3j82blcq]
- FC 4.0[/*:m:3j82blcq]
- CC 0.0[/*:m:3j82blcq]
- pH 7.6 (it's usually 7.5 and the auto pH system was adding some acid on Saturday, so I assume it's 7.5 again)[/*:m:3j82blcq]
- TA 60 (it's usually been 70; I had another test a few weeks ago that was down to 60, but then it went back to 70 so I didn't do anything)[/*:m:3j82blcq]
- CH 450 (I just have hard water; I replaced about 50% of the water last year to try lowering CH, but it's back)[/*:m:3j82blcq]
- CYA 90 (Higher than I want. I added some stabilizer about 3 weeks ago and by the measurements, I didn't expect it to get as high as it did. I thought I'd end up around 70. This surprised me. Could this be related to algae? If nothing else, it's going to take more chlorine to shock it.)[/*:m:3j82blcq]
I brushed the pool on Saturday morning and didn't notice much of anything cloudy.
A couple of weeks ago I suspected algae, as I brushed the pool and stuff was coming up. It was hard to tell if it was algae or if I got some dirt from winds (I live near a ball field which is sometimes a source of dirt in my pool). I brushed it and it cleared up and I didn't really notice much more after that, so I concluded it was just dirt, especially since FC was pretty constant.
My only thought is looking at the Shock/CYA Chart is that target FC is higher with the CYA up where it is. Do I just need to shock it and keep my FC level higher because my CYA is high?