How often should I change my aquarium media in my sump?
you should not be running any media other then bioblocks / live rock.
Carbon should be off, skimmer off.
You want your water to get as dirty as possible in a controled way though cycle.
But what media are you exactly talking about?
Carbon? GFO? Rox Carbon? Purigen?
And are they just in a baggie dropped inside the sump or you using some form of reactor for each of them?
Also how i ended my cycle was i waited for Ammonia to drop to 0... then nitrite to 0.
Then i dosed the tank once more with 2ppm Ammonia, and recorded how long it took for nitrite and ammonia to go back to almost 0.
Then i did a 40% water change.
Turned on skimmer, turned on my reactors, put in my filter socks and polyfilters, fired up the Chaeto reactor, and did a seed on copepods.