Many brands of carbon will leach phosphate, I have been told they all will, it is just a matter of how much. There is no such thing as FW
and SW GAC
. Kinda reminds me of when I was on the track team and I told the new guy to get me the left handed shot put. :P It is a lesson we have all had to learn, you can still use carbon, but it will become bioactive within a few days (the idea is to have all nitrification happen in the tank, not a filter), and it's ability to adsorb DOC
, and toxins is used up within a couple of days anyway. All it really does is remove yellowing agents from the water after the first few days.