Replacing GAC schedule while dosing Ozone

[demariners]

I am wondering how often I should be replacing my GAC when using ozone? Once a month? Any suggestions on this? Thank you.

[cantonreef]

Is the output from the ozone running through the GAC?

[demariners]

Well sorta. I have the skimmer output in the sump which then goes to the return pump. Was going to put carbon in a filter from the return line,