Filtration Basics - Chemical Filtration and Reactors

When the topic of filtration comes up in regard to aquariums, there are three categories: Chemical, Biological, and Mechanical. Today, we'll talk about chemical, and get into the other two categories in coming weeks.

Chemical filtration utilizes specific media or materials like activated carbon to your filter system. The structural nature of these materials remove pollutants or colorants from the water, making it cleaner and clearer. There are lots of different substances that can be used to chemical filtration. Some of these, like activated carbon, are generalists, grabbing basically everything it can out of the water indiscriminately. Others are very specific and only hunt for specific compounds, for example Tropic Marin's Elimi-phos is very useful for reducing phosphates in aquariums, but doesn't act on anything else. These kinds of media are generally used in areas of high flow in filter systems. They can be a part of a canister filter, or they can be bagged in a sump, or they might even have their own dedicated system called a “reactor.”

Very simply, media reactors are just a tube that has have plumbing and a screen on both ends; water gets pumped into the bottom of the tube very slowly so that the media (whatever it is) just barely is agitated on the surface as the water passes through it. The water then leaves the tube through the top screen and gets sent back to the aquarium. This allows for a very thorough exposure between aquarium water and filter media. Most media should be replaced on a regular schedule. Reactors are very handy for rinsing media as well because you can just run water through them in the sink and wait for the water to run clear.

Our partner stores can all buy the V2 Bio-React 500 from us, which is a reactor good for a wide range of aquariums size. It works a little differently than the usual “up-flow” design in that it utilizes a unique flow inductor that keeps media in suspension extraordinarily well, maximizing contact time between water and media, and insuring good circulation within that media. It can be used in sumps, or even as a “hang on.”

The most popular chemical filtration (by a large margin) is activated carbon. Activated carbon has been used to filter just about everything liquid that humans have touched in the last two thousand years. We filter drinking water, alcohol, we even purify gasses with it. It can be made out of just about any wood, and even coconut shells get turned into activated carbon. On the upside, it removes just about everything you need to worry about in an aquarium, and polishes the water to a great degree. On the downside, once the carbon is saturated, it may start to leach some of the pollutants that it removed back into the system. It is important to replace activated carbon on a regular schedule. Always buy high quality activated carbon, as it will be cleaner, have less dust and last longer. Even with very high quality carbon, you will need to rinse it until dust stops clouding the water you're using to rinse it. Carbon dust can be very irritating to fish and inverts.

The next most popular chemical filtration that you'll frequently see is something called GFO, or granular ferric oxide. It is an iron oxide hydroxide that comes in little clumps. It is popular for removing excess levels of phosphate. It is best used in a reactor, and needs regular replacement. It is very inexpensive, but also has limited effectiveness. Always buy the best GFO you can, it will last longer, and be cleaner. Just like activated carbon, you will need to rinse the GFO thoroughly before putting the reactor back into service. When using GFO, hobbyists decide when to replace it by monitoring phosphates in their aquarium. When levels start to go up, they replace the GFO.

Another popular way to control phosphates in a reactor is Elimi-phos, from Tropic Marin. It only addresses phosphate, and doesn't leach once saturated. It works quickly and efficiently. In our experience, your aquarium shouldn't have a regular phosphate issue, and if it does, you should be investigating where that phosphate is coming from. Likely sources are food, salt and water supply. Once you've worked out where your problem is, you won't need regular treatment like consistently running GFO, but you might need a short term solution to deal with the problem, and Elimi-phos in a reactor is our recommendation for this. Another great short term spike fixer is Tropic Marin's Elimi-NP, which can help you alleviate spikes in nitrogen as well as phosphate. This is great for over feeding events, or when adding bioload to an established system. We don't suggest either for long term use, with some very distinct exceptions, but both products work extremely well for combating nutrient spike issues.

Another very popular generalist is Seachem's Purigen. This is a useful media that has little to no effect on trace nutrients in the aquarium, while still removing a huge range of pollutants, colorants and nutrients. Its one of very few chemical media that also help control nitrogen based compounds like ammonia, nitrite and nitrate. It can be used in filter bags in a sump, or canister, but is also best used in a reactor. It polishes water to a sparkly degree and changes color as it exhausts, so you'll know when to change it. It can be renewed with a fairly easy process that you can see in a variety of videos online.

There is a wide variety of other chemical filtration available to you as a hobbyist, however, in our experience, most well balanced aquariums don't need much in the way of specific filtration, outside of specific incidents. Perhaps you strayed from the path, and started using a cheapo salt mix and you ended up with a phosphate spike. Well, you're going to need to come back to the good Tropic Marin salt, and you may need to treat the display with some short term chemical filtration like Elimi-Phos.

Conversely most aquariums will look brighter if some generalist type chemical filtration is used in a gentle fashion. You don't need a ton of carbon or purigen, but a little of either can make a huge difference in just how sparkly your aquarium looks on a daily basis. If you love that “fresh water change look” and want it all the time, perhaps a media reactor and a little activated carbon should be on your list. Head over to your Local Fish Store, and ask them about getting you a V2 reactor from Quality Marine and whatever else your aquarium could use!