Hello, as my title implies, I am trying to find the best bio media available to purchase, not factoring in cost. I have done my research and realize that different medias have their benefits and drawbacks. However I was wondering if anybody could give me some advice because I have not dealt with filtration for large tanks before. My ideal media would be extremely low maintenance, keep water changes(nitrate) to a minimal, and be able to handle a large bio-load for its size and then some for added insurance. I currently have a 550 gallon tank that I am finishing up the plumbing and sump on. My stocking list will most likely consist of a freshwater stingray(Marbled or Motoro most likely), 6 discus, an silver Arowana, and a Ornate Bichir. I have up to this point been cosidering a fluidized bed with k1 kaldness, however the air pump energy cost is a small drawback. I have also heard great things about matrix but I am weary about any product that claims to do it all in a small cheap package. Bio-balls are neat idea, but I have heard if they are not cleaned abundantly they will increase nitrates heavily. Anybody with experience with large tank filtration have any opinions/advice?