Thanks!! The pump is a Hayward SuperPump if that helps any. I just checked and adjusted the cl- to 20; it was between 15 and 20. I'm going to let it circulate for another half-hour and shut off the pump. I agree that the dead algae is going right through the filter. The first few days I was needing to backwash every few hours; now the pressure rises maybe 1-2 psi over the course of the day..even with the DE added. I will report back with results on your recommendations. Once again, thank you so much.
Stella