My pool was easily cleared this year. I kept the filter running 24/7 and brushing away dirt/algae toward the drain. It keeps coming back. Primarily building up around the return jets and steps but always a fine blanket throughout the pool. I turned off the filter to see what the case would be and it seems the algae is just blanketing the pool when the filter is running. Question is, should I replace the sand in the filter its been more than 5 seasons. Is it a standpipe and lateral issue possibly or do I just have to keep the filter going continuously still and keep brushing? It doesn't seem to be filtering the dead algae out.