When I opened my pool I could see the bottom, but water wasn’t very clear. There was no sign of algae – I made sure to prevent it by circulating chlorine with a sub pump a week or two before opening. The water got crystal clear in two days or so and after about three days the DE filter pressure went up by 8 and then it dropped again by 6, so it’s now 12 instead of the original 10. I wonder why the pressure went up and down and if I should backwash no matter what the pressure is now.