In the Fluval 204...there is a "media basket tray" in the top basket. Its not the actual media basket, its a tray that sits inside the top basket. The manual didnt say much about it other than its name. So im thinking that it is used kinda like a seperator? The reason why i am asking is because im going to put polywool type stuff in the bottom basket, carbon in the middle basket, and biomax in the top basket, well i have too much biomax to fit underneath that tray.(the biomax takes up the whole basket) So my question is, what is it used for?