I've been using TFP for 2 years since we moved to our new house, but we just got an algae breakout. Not bad, but a definite green tinge to the water, especially noticeable in the deep end. I had been running my FC around 3.5-5 or so and my cc was always <0.5, if not 0.
Anyway, we came back from a week with the cover left on and:
1. Mixed up the Cl test and thought the FC was too high, so turned down the SWG clorinator.
2. Somehow forgot to turn on the main drain after vacuuming, leaving just the skimmer for 2 days.
3. FC fell to 2.5. I figured out what I was doing wrong with the FC test, restarted the main drain. 2 days later, green water. I'm surprised because the FC never went below 2 and the FC went to 1 last year for a couple of days with no breakout before I got it going again (neighbour accidentally turned off clorinator)
pH 7.5 FC 5 / cc 0.5 / CYA 50 / TA 110 / CH 150
4. Shocked up to 20 overnight and vacuumed pool. Guage went from 12 (usual) to 17, so backwashed.
Tonight, pH 7.6 FC 10 / cc 0.5 / CYA 50 / TA 110 / CH 150
5. Will Shock up to 20ish again. Hopefully pool will be OK for the weekend.
(I'd been fighting with the pH to get it up all summer, now it's too high from the shocking with bleach)