Canister filters have been around since the 70’s. They have been used successfully on all sorts of different aquariums, including freshwater, planted, brackish, saltwater, turtle tanks, reef tanks and more.
Some characteristics of canister filters make them less ideal for reef aquariums. However, with proper maintenance and usage, it can still be used very successfully and cost-effectively.
The main reason to not use canister filters for a reef aquarium is that they tend to be a nitrate trap. Over time, detritus and gunk build up in the canister filter. These trapped organic mater then breaks down into undesirable nitrates and phosphates that can be detrimental for your sensitive reef aquarium inhabitants.
However, if you are able to keep up with the regular maintenance of your canister filter and keep the trapped organic matter to a minimum, a canister filter can work very well to provide mechanical, chemical and biological filtration for your aquarium.
Aquarists often ask what kind of media can be used in their filter and how the media should be placed inside the canister. Every filter manufacturer has their own recommendation for media and how it is positioned in the canister. Regardless of the model, there is a logical “order of things” to consider when loading your canister with filter media.
Mechanical Filtration First
Mechanical filtration clarifies the water while protecting the other filter media from clogging with debris. Mechanical filter media include foam pads, synthetic fibers and other mesh type materials.
Eheim canister filters use EFISYNTH filter floss and Coarse Filter Pads for the ECCO series. The FilStar XP canister filters use coarse foam pads followed by fine foam pads. The idea is the strain out the larger particles first, then trap the small particles. Most mechanical filter media can be rinsed when dirty and used again. However, for a reef aquarium, replacing the filter pads is preferred to minimize organics. Filter-specific pre-cut pads make it easy to get optimal debris removal.
Chemical Filtration Second
There are many kinds of chemical media including activated carbon pads, bags of carbon-resin blends, and phosphate removers. Loose filter media can be placed in filter bags. Pre-bagged media, like the AquaMaxx AIO, will drop into any canister filter and provide superior chemical filtration over activated carbon alone. Chemical filtration is normally used for about 30 days and discarded. Once the media has absorbed as much as it can and/or get covered with dirt and bacterial slime, it will no longer remove pollutants.
Biological Filtration Last
Biological filter media provide a surface for beneficial bacteria to attach and form stable colonies. Bio-filter media come in a variety of materials, shapes and sizes. Eheim SUBSTRAT Pro are porous beads. SeaChem Matrix uses an inorganic solid material that is extremely porous. No matter which you select, biological filter media should be protected from debris so it does not get dirty and clog up. Unlike other filter media, biological filter media does not need to be replaced every month. If it looks dirty, just rinse it in some aquarium water. Don’t allow bio media to dry out when you service the canister filter. It could harm the bacteria on the media.
Polishing Up Your Water
The last, and optional, stage is the polishing stage. You may want to use a final polishing filter to really make the water sparkling clear. The Cobalt Aquatics EXT canister filter comes with a 4th stage finishing floss that removes the finest particles. There are many cut-your-own filter pads to choose from. Just cut the pads to fit your brand of canister filter. Be aware that polishing filter pads can clog very quickly and dramatically reduce the flow rate. Keep a close watch on your water flow when using polishing pads.
Change Your Filter Media Often
Mechanical and chemical filter media does not last forever. Eventually it will clog with debris and lose its effectiveness. Additionally, organic matter gets trapped and accumulates over time. You’ll notice the water flow rate slows down as the canister filter gets dirty. Never let your canister filter get “gunked up” with sludge! For saltwater aquariums, you will want to replace the mechanical and chemical filter media monthly. For freshwater aquarium, you can change out the chemical filter media monthly and simply rinse/clean out the mechanical filter media. If you take care of your canister filter it will keep your saltwater aquarium healthy and looking great!