I use it in my quarantine tanks HOB, it works. It is a bio media providing surface area for nitrifying bacteria growth. It is not effective until colonized by nitrifying bacteria. It does not replace carbon. Carbon is a water clarifier/chemical media that absorbs pollutants and gets used to capacity.They work well together.
For instance matrix stays in to keep the tank cycled while I run Cooper in quarantine, carbon goes in if I need to remove the copper from the water. Carbon needs to be replaced on a regular basis, matrix does not. I continually run matrix, I run carbon as needed for water clarity or chemical removal.