When I run carbon, it is inside a mini-canister. It's the Rapids Mini-Canister.
Canister Filters: Rapids Mini Canister Filter at Drs. Foster and Smith
I use fine mesh media bags. The 3x4 size fits this canister perfectly.
Aquarium Filtration & Filter Media: Drs. Foster & Smith Fine Filter Media Bag
It takes about 2 cups of carbon to fill the bag. Tie the bag shut and rinse it in RO/DI water to remove the dust from the carbon. Stuff the bag in the chamber. Prime the canister and plug it in.
I run it for about 3 days and then dump it. Dump the carbon right down the kitchen sink. The garbage disposal chops it up pretty easily. Wash the media bag and set it out to dry. Wash the canister with hot tap water and dry it with a paper towel.
If you want to run the carbon all the time, just dump the bag, wash it under the tap and then refill it with new carbon. Rinse the carbon in RO/DI water to remove dust. Stuff it back in the canister and run it for another 3 days.
Rinse and repeat.
I dump it every 3 days because the bags get slimy. Thats organic waste that collects on the bags. If you leave it in there, eventually you'll start growing aerobic bacteria and converting the organic waste into nitrates. Nitrates go up - algae blooms, corals suffer -- big doo-doo - bad joo-joo.
So dump it every 3 days and wash all the goop off the bag. Rinse the canister in hot water. It goes without saying - DON'T PUT SOAP IN YOUR CANISTER TO WASH IT OUT!!! Hot water will work fine. This will stop the growth of aerobic bacteria and therefore inhibit nitrates.
The canister filter isn't really a filter IMO. It's a water pump with a reservoir. You can use that reservoir for mechanical filtration or chemical filtration. But if you don't clean it OFTEN it'll turn into a biological filter. Thats BAD. You want your live rocks and DSB to take care of your biological filtration. The live rock and DSB will handle the nitrates naturally. They will eat and convert the nitrates into harmless nitrogen gas that bubbles out at the water surface. A canister being used as a biological filter will only produce nitrates. Thats all it can do. There are no anaerobic
(low oxygen) areas inside a canister. There is no way to grow the anaerobic bacteria needed to reduce the nitrates into nitrogen gas. So it just makes nitrates that put an extra load on the rest of your biological filter.
One of the WORSE
"filters" in the aquarium industry IMO. Use it for what it CAN do. Mechanical and chemical filtration. Do not allow it to grow bacteria.