As with most topics surrounding reef aquariums, the use of activated carbon in a reef aquarium brings controversy, opinions, concerns, and accolades.
Activated carbon for the aquarium is carbon (mostly from coal or lignite) that has been treated (heated or by chemicals) to increase the amount of pores, thus increasing its absorption ability.
Why is activated carbon used in the aquarium? In short, activated carbon is considered a form of chemical filtration and used by aquarists to removed organic compounds including colors, chemicals, medicines, and toxins from the aquarium. The protein skimmer can do a really great job at removing impurities in the water, but activated carbon goes to a whole new level of filtration. For example: There are organic compounds in water that give aquariums a yellow tint. Activated carbon can remove this yellow color and make the aquarium look much more blue, also allowing more light to get to the bottom of the tank and to corals.
Some aquarists may argue that there is no activated carbon in the ocean, so why use it in the aquarium? What I am finding the response to that question to be is that the ocean is so vast and has such a large surface area it allows thousands of species of organisms to grow and process any over-abundance of organic wastes, maintaining a perfect balance. The home aquarium may look like a mini piece of the ocean, but in reality we must use and maintain a host of mechanical, biological, and chemical filtration just to make owning a reef aquarium feasible. Even the salt we use is synthetic. The lighting formulated for the best possible coral growth. A home aquarium is not self sustainable like the ocean is.
The next debate over the use of activated carbon is in how often to use it. Some aquarists use activated carbon 24/7, others only use it once a month, or once every few months. The concerns over using activated carbon continuously is the thought that the carbon will not only remove organic wastes, but also the trace elements from the synthetic salt mix that the fish and corals need. From my reading however, activated carbon does not remove trace elements from water because this can only be done at a pH range outside of the range reef aquariums are kept, and many aquarists with successful reef tanks that use activated carbon constantly can attest to this.
Another concern is that activated carbon can leach phosphates into the water causing excessive algae growth. This is true that some carbons will leach phosphate because the phosphate is either naturally occurring in that type of carbon, or is part of the treatment process of activating carbon. However, not all activated carbons contain phosphates so simply switching carbon types or brands is the solution.
There are many other questions and debates concerning the use of activated carbon, but the ones mentioned above seem to be the main concerns. With all of this in mind, we decided to use activated carbon in our tank, at least for a little while to see if we noticed any benefits.
We selected the best activated carbon from Bulk Reef Supply Company, the ROX 0.8 High Performance Aquarium Carbon.
The Bulk Reef Supply has some great videos on their website about many of their products, one of which is a demonstration of their activated carbon at work. These videos are a great resource in learning about how products work, even if the product is not purchased from Bulk Reef Supply. That being said, we have found that not only is the BRS very informative, they have great pricing as well. We have purchased only a few things from them, but have been very satisfied.
Once the carbon was rinsed to remove any dust, we placed the designated amount for our tank (0.56 cups per 90 gallons) into a mesh bag. We then placed the bag into the sump, next to the return pump. Carbon reactor canisters can also be used, but for now we chose a simple mesh bag.
What we noticed within a short period of time was how clear and blue the tank looked. The yellow tint (gelbstoff) from dissolved organic compounds was removed very quickly causing the tank to look pristine. How often we use activated carbon will be determined after our test run. I have read both sides of the argument, and know that there are aquarists with successful tanks that never use carbon and those that are never without it. For now we will keep an eye for any adverse reactions and simply enjoy our very blue, very clear aquarium.