patch of yellow algae but pool was balanced???

[avidone1]

This morning I got up and noticed a patch of yellow algae on the base of one wall. I tested the water and pool chemistry while not ideal seemed ok
enough not to start algae growth. specifically the readings were;
Chlorine - 2.0
PH - 7.5
Total Alkalinity - 60
hardness = 350
stabilizer - 40
water temp - 83
pump running 7 hours daily.
Weather conditions have been hot and rainy lately.

The patch was small, about 8-10 inches in diameter.
Any ideas as to why this algae bloom started?

 

[jblizzle]

Your FC is too low for your CYA level. Is there good circulation where it appeared?

 

[Richard320]

Scrub that algae and get some bleach in there, fast. If you don't kill it, it will start growing and using bleach even faster.

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[avidone1]

Oh I scrubbed it and dumped in a full jug of bleach......this morning no algae. Like I said, it was just starting.
I rechecked my cya level, and it was around 50 not 40 so I think that my fc was too low for the level of cya.
I have to relearn every year that as the weather warms I have to increase my vigilance.....Got off easy but LESSON LEARNED!!!

 

[jblizzle]

With a CYA of 50ppm, your FC should never be below 4ppm ... so should be targeting 6-7ppm everyday: See the FC/CYA Chart.