Lets go back a little........... you have a fusion 30L or 30G?
Either way I would try your skimmer first and water changes before I jump on the GFO train.
Yes randy is right that you need some sort of phosphate export but GFO is IMO super aggressive.
Of course with the proper use of it you will come a long way.
But why not save here some $$$$ and go a long with a water change first.
It's easy enough to hook up Carbon and GFO but IMO not needed at all.
First get your tank wet and go a week or 4 through your cycle, while doing that test with a trusting test kit (not api) for ammonia, nitrite first and move over to the nitrate, phosphate and PH.
Good luck my friend.