Saltwater aquarium reactors and contactors
If you’ve spent any time online exploring reef discussion groups, shopping online or hanging out at a good reef shop, you’ve heard about or seen alien-looking devices called “aquarium reactors” or “contactors.” Depending on your temperament, your first response to reactors might be “COOL! I want one…or two!” or “Looks complicated and scary.” Before jumping to conclusions (or pulling out your credit card), let’s explore what aquarium reactors and contactors do and how you can benefit from having one on your reef aquarium.
What’s the difference between an aquarium reactor and an aquarium contactor?
Over the past 20 years, a lot of saltwater aquarium gadgets, gizmos and gimmicks have come and gone, but aquarium reactors and contactors are solid pieces of aquarium equipment that have stood the test of time. Even though the term reactor is the more common term (and is sometimes applied casually to mean either a contactor or a reactor), they are different.
A contactor is a device that has been designed to maximize aquarium water contact with the media you put inside the contactor. A contactor is typically an acrylic tube that filled with media, like phosphate remover. With a contactor, you simply load the filter media and adjust the flow rate through the tube to maximize contact with the water.
Why is this desirable?
Simply put, filter media only works when the surface of the media is in contact with aquarium water. If you just placed a pouch of media indiscriminately in your sump, the media would remove some contaminants, but the surface of the media would quickly become clogged and the media would only remove a small number of contaminants.
A contactor, by comparison, enables you to use a large amount of media, in a confined space, and make maximal use of the capacity of the media. Contactors are frequently used in a saltwater aquarium for removing phosphate and nitrates from the aquarium. These devices isolate the denitrification or phosphate removal processes from the rest of the aquarium. It can be as simple as slowly flowing water through a porous biological media, creating a low-oxygen zone where denitrifying bacteria reduce nitrate to nitrogen gas. More advanced denitrators contain carbon or sulfur pellets that stimulate the bacteria and promote denitrification inside the contactor.
Contactors are usually simple devices where a small stream of water is diverted from a canister filter or main pump and into the contactor. The flow rate is controlled with a valve. Some advanced denitrators have their own water pump, making it easier to use with a sump system.
By comparison, aquarium reactors are similar to contactors but operate by a slightly more sophisticated functionality. You might have guessed, by now, that the name aquarium reactor gives a small hint as to how they are different from contactors. As the name defines, a chemical reaction is going on inside the reactor. You could argue that denitrification is a “reaction” too, and it is, but it is more biological than chemical. But chemicals are involved in the cells. Umm…let’s not go there now. So what is the reaction part? Calcium and carbonate! Every reefer knows soluble calcium is important for corals and proper buffering with carbonate stabilizes the pH. There are liquid and powder products that help aquarists manage calcium and carbonate levels. The idea behind calcium reactors is to keep the water chemistry stable and constant. Instead of having the calcium level fluctuate in-between liquid doses, the aquarium reactor automates the process and maintains a steady calcium level.
How Calcium Reactors Work
A calcium reactor contains a large amount of calcium-rich media, like aragonite. Aquarium water is slowly pumped through the reactor along with pressurized carbon dioxide gas. The carbon dioxide gas reacts with the water to form carbonic acid. This lowers the pH in the reactor and slowly dissolves the aragonite. Soluble calcium and carbonate are released into the water and flow into the aquarium. The steady stream of calcium keeps the reef supplied with the right level of calcium and carbonate. Reactors require patient adjustment to dial in the necessary pH and flow rate.
Aquarium contactor and reactor media
GFO (Granulated Ferric Oxide)
For removing phosphates, the most popular media is Granulated Ferric Oxide (usually abbreviated GFO). PhosBan is a specific brand of GFO sold by Two Little Fishes.
Calcium Reactor Media
As mentioned earlier, the media used in a calcium reactor is generally small pieces of calcium carbonate rock. The Two Little Fishes brand ReBorn is a calcium carbonate media made from fossilized stony corals, but there are also many other (often less expensive) products available.
Activated Carbon Media
Activated carbon has been used as a filtration media in the aquarium hobby for a very long time. While not as interesting and en vogue at the moment, it does a commendable job at removing unwanted chemicals from your aquarium water and works great in a contactor.
Should I get an aquarium reactor or contactor?
Although there is an initial investment and learning curve, many reef aquarists say it is worth adding an aquarium reactor. Once dialed in, reactors require almost no maintenance and they help you maintain better water parameters. And don’t forget the “Wow Factor” when you show your friends! If all this sounds fun and exciting, a reactor is definitely for you!
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