A few weeks ago we came back from vacation to find a family of ducks in the pool. We got them safely relocated, but were left with algae on the walls. I've shocked, brushed, backwashed and vacuumed a few times, but it still keeps coming back.
Currently I've got very high Free Chlorine of 17.25 ppm (due to three shocks in the last two weeks) but algea still grows. (Shouldn't that chlorine level prevent further growth?)
My pool store keeps advising algaecide, but everything I hear saiys it's bad for the filter.
Should I try to shock harder? Do I have to deal with the CYA? (I'd rather not drain the pool.) WILL algeacide help?
I'm at a loss for what to try next. Any advice is appreciated.
Here are test results (from pool store - Anthony & Sylvan, which uses electronic testing):
FC: 17.25 ppm
CC: 0 ppm
TA: 74 ppm (have been advised to raise it
CH: 200 ppm
CYA: 100 ppm