I have two Emperor 400s on my 75 gallon tank. After reading so many don't use the carbon cartridges, I have tried to switch them up. Since February, I have been running them with the following: Coarse black filter foam, bio balls, bio max, polishing foam plus the total of 4 bio wheels. I have no idea why I chose these so now I need to know if this is ok or if I should do something different. To be honest, I don't even know what any of this does or if I am missing something that my tank needs. Other than the polishing foam, does any of this need to be replaced as it becomes old?