Good to hear it's a big tank. Btw, you don't need carbon. It used to be thought it was needed but new research shows it's not only NOT needed, but can sometimes do harm. So today it is not much used by most experienced fish keepers unless they need to remove odours, colour or some meds from water, and then is used only until the needed job is done.
Unfortunately, most filter manufacturers continue to put carbon into their 'refill' cartridges, and people use them, perhaps not even knowing the carbon is there. And if they don't change those cartridges often enough, the carbon can discharge what it has adsorbed, if it's left too long unchanged.
It is best replaced by extra bio media, which will do much more good than carbon does. If you want to use it, you have to be aware it becomes exhausted within a few weeks, and must then be replaced. Once exhausted, then it can release all the organics it's adsorbed back into the water, where they may cause harm.
I have it in case I need it, but never use it as a routine media. I use it more for orchid growing than anything else.
