I'm hoping someone can help me with our algae problem. First I'll provide some background.....we had a 27' above ground pool installed last Spring (2011) and had absolutely no problems keeping the water sparkling clean using bleach. This summer we are using the same method and the pool is constantly turning green/brown. Nothing has really changed.....we're using the same sand filter and pump and testing using the same TF-100 Test Kit.
The only time I've been able to keep it clear is when I keep the FC level near shock level (around 14). As soon as it drops down, the water starts to turn cloudy and within a day or two it is greenish brown. For example, I had the FC up around 14 a couple of days ago. I didn't check it for a few days (the solar cover was on and the daytime temps were in the 70s). I took the cover off yesterday and the water was greenish/brown and there was a layer of greenish/brown "dust" along the bottom. I checked the chlorine and it was at 5.5. I've had the FC level up at shock level for a week and still had issues afterwards. I've even added DE to the sand filter as specified on the website to clean up the water. Below are the other average chemical levels throughout the summer:
pH - 7.5
TA - 120-130
CYA - 40
Could this be mustard algea? Why would I have it this year and not last?