Swimming pools blog

Basics: 25k gallon, in ground, 20 year old pool. The pool is mostly
shaded by several (too) large trees. This week (not all summer) I’ve
been getting a lot of green alge growth in the sunny areas of the
pool. I sweep it off (using the brush not a pool vac) and run the
filter overnight, but the next day it’s back! My ph and chlorine are
at good levels (chlorine is even a little high some days), I add
algecide etc, but can’t keep it from growing….
Suggestions?
SEC