I'm currently in the process of building a new vivarium and one knowledge gap in particular struck me to me and cannot be resolved by looking at images others' builds. With Matala mats, no water is absorbed by the mat itself and passes through easily. But what about the finer filter foam that is placed on top of the Matala mat? From the images and the words used it look like aquarium foam which, from my understanding, will first absorb water until it's full before letting it pass through. Is this actually the case with the product that's we're supposed to use? Or am I misunderstanding and they're some different product entirely, one that is like the Matala mat and let water flow through immediately? Thank you.