corrugated plastic

I am slowly but surely getting my Waterbox INFINIA Reef 190.5 set up after my RedSea seem broke over the summer. I finally have everything solved, but the Waterbox overflow and ReefMat are giving me trouble. The ReefMat makes a loud washing machine noise. I can see the bubbles in the unit...

Is Corrugated Plastic reef safe in the water? Going to use it to make a stand for skimmer as I have some laying around already.