Pollen or algae?
Pollen floats and collects along the downwind edge and in the skimmer as a yellow film; mustard algae clings to walls and does not move. Pollen rinses off your hand, mustard algae smears. Both show up in March under pines in Woodlands, Spring, Tomball and Cypress.
The routine that works
Empty the skimmer basket daily during the peak two weeks; a full basket stops circulation. Run the pump longer, and net the surface in the afternoon when pollen settles. Keep chlorine at the high end of range because pollen is organic and consumes it. Expect to clean the filter once at the end of the season, because pollen is fine enough to pass a dirty basket and pack the filter.
If it is already yellow-green
Brush walls, shock once, and run the filter continuously for a day. If the color comes back within days, it has become mustard algae and needs a proper algae treatment.
Questions
Does a pool cover help with pollen?
A solid cover keeps most of it out, but pollen still enters when you open it and the cover itself needs cleaning. Frequent netting is usually easier.
Why is my filter pressure high in March?
Pollen. Clean the cartridge or backwash, and plan a full filter cleaning in April.