I don't know which one is best but I can tell you which one I use. I use black diamond carbon, not the most expensive out there not the cheapest. I run carbon one week out of four. before one of my large water changes that way I soak up as much as possible then dilute it even more with the water change, also so as not to absorb anything I might be adding during the water change. I place it so all the water that flows into my sump is forced to run through it(open topped bag the water falls down over it) The only draw back would be that by doing it this way any pods that get pulled down the overflow get removed with the carbon, but I consider it a negligible loss.