To the OP what size tank is it and what fauna do you keep?
I use Rowaphos and carbon every now and again in separate reactors but adopt the WWC method of 5-10% water changes every week regardless of tank size.
I have tangs so try and use carbon sparingly as it can cause HLLE.
Carbon is only good for about a week before it needs changing regardless and running it constantly is just wasting money. Use it to get your water sparkling then ditch it.
Another question are you using filter socks and if so how often do you change them and what micron are they? A decent regime and 200 micron or less will take out a lot of organics.
Making sure your protein skimmer is working correctly also will help, a nice wet skim to get things moving in the right direction would improve your water quality also.
Lots of variables.