I just noticed, for the first time, excuse my noobness as this is all new to me, but there's a barrier in front of the skimmer where the filter is. And this barrier can slide up and down. I noticed it was up almost all the way, so when I slid it down suddenly a lot more water was going in there. What should I do? Should the top of the barrier be a bit below water level or should it be all the way down? Thanks!!