Hello. Can someone explain to me what is the BEST way for me to be setting up my canister filter. I have a cascade 1000 and I feel like I am trying all different ways to layer all of the media and I don't know if I'm doing it right. There are so many things that I am still learning. I have 3 RES turtles in a 55 gallon tank (I know it's small but it's all we can fit right now in our house). I take excellent care of them. But the all of the filter stuff confuses me.i don't know what's chemical or mechanical or bio whatever. What SHOULD I be using. And do these three things serve the same purpose?