Activated Carbon...What is it? Do I Need to Use it?

Activated carbon is a powerful tool for achieving and maintaining good water quality. Carbon removes off-putting smells and yellowing compounds from water.

Activated carbon is frangible, which means brittle or fragile. This means that you can crush it into powder easily and create dust. The carbon dust is what you don’t want inside your aquarium as it has been implicated as a possible cause for an ailment called head and lateral line erosion (HLLE) in fish. In the single study that has been done on carbon, the study suggested large amounts of carbon dust from unwashed carbon caused HLLE. No need to treat carbon dust like it was a radioactive isotope, just rinse it until the rinse water runs clear, don’t tumble it and your fish will be fine.

What is the best way to run it in your system? My two favorite methods are using a media reactor or a small, zippered media bag in a high flow area of the sump.

Running it in a media reactor allows you to place a sponge on top of the carbon inside the reactor to keep it from tumbling and turning into dust. Running it in a small, zippered media bag placed in a sump baffle or other high flow area is also a great way to run carbon too. Keep in mind running carbon in a bag is a passive method meaning you aren’t pushing water through the media like in a media reactor. Passive methods are less effective in removing wastes from your tank’s water, and they require less equipment which some hobbyists like. When I run carbon in a bag, I use a smaller amount because a large bag of carbon run in a passive manner will have carbon in the core of that bag never even come into much contact with your tank’s water.

No matter if you use a reactor or a bag, you definitely don't want it tumbling around in a media reactor or getting battered by water motion in a loose bag.

Studies have also shown that activated carbon will generally become exhausted around two weeks time. That is very dependent on amount of carbon, the quality and how you are employing it. I have always liked the idea of running a smaller amount and replacing it frequently. Every two weeks I replace the carbon on my tanks taking extra care to rinse the new carbon before it goes in my tank.

Whether a reef tank or fish-only system, carbon is an extremely effective way to keep your aquarium looking clean and smelling better.