Hello, carbon really does not do a whole lot. If you have plenty of gravel in your tank and/or a filter dedicated to growing your beneficial bacteria you will be fine without carbon. Even if you buy carbon its only active for about a few days at most. If you have odor from a neglected tank carbon can help or if you have introduced certain medicine to your tank and need to remove it you can use carbon for that as well. You really do not need to get into any habit of using carbon unless it just comes with your filter media bag.