JULLES --- the roots on those philadendrums are like stong, ropey, runners that span out from the main plant. They were seeking water, growing across the top edges of the perimeter lining and squishing it down. What once was above water level was now well beneath. I took the liner and pulled it back up into a vertical orientation. I then took the rock and moratared on both sides of the liner, "sandwiching" the liner between the moratred rocks to the inside and outside.
Also, correctly setting the skimmer to the recommended height with a footer of mortar and block as well as it's sides will keep it level and in place for years and years to come. Before, it was severly tilted and WAY to low. The pull on that skimmer before was weak as it was drawing in way to low in the water column.