I don't want to debate if carbon dosing reduces nitrates only or reduces both nitrates and phosphates. There is info out there saying it only impacts nitrate levels and does nothing for reducing phosphates and then you'll find the same amount of other info saying it impacts both NO3 and PO4. Also, I've seen a lot of awesome reef tanks utilizing both carbon dosing and some type of phosphate removal media and a lot of awesome algae free reef tanks utilizing carbon dosing without any phosphate removal media whatsoever. Whether one is true and the other is false or not doesn't concern me, what I want to know is . . .