you have more filtration then just the mag right?? I'm sure you do, at first glance it seems like that's all you had on a 210g
I'm no expert but first of all, tell the qty of fish and what size are they in the tank. This will give people more info and that will be better for them to advise you,....... personally, I dont' even use carbon,...........
and second, I'm assuming you're new here, it happened to me too when I first started, you're posting in the wrong forum. go to "setup and filtration". All the pros there will be more than happy to help you out