Regarding the Use of Canister Filters in Saltwater Aquariums

Tropical fish aquarium

Canister filters are used in saltwater aquarium systems for mechanical, chemical, and/or biological filtration. A can be used on a continuous basis or added and utilized as needed. They can be used as a standalone filter or in conjunction with other filtration methods. For each category, below are several instances.

For Mechanical Filtration

A hang-on-tank canister filter can be added to a system with an under gravel filter to eliminate free-floating particle matter from the water that would otherwise be dragged down into and trapped in the substrate. This style of aquarium setup helps to enhanced water quality by continuously operating a canister filter.

An aquarist with a semi-reef system with fish and live rock can use a canister filter as a "pre-filter" to remove unwanted waste, particulates, and detritus from their tank water before it passes into or through their biological filter (i.e. wet/dry trickle) or main tank water supply, such as into a sump. This can also be done on full reef tanks with live rock and corals, although the issue about running mechanical filtration in this sort of system is that it filters out important plankton life in the water, which many marine species eat.

Hang-on-tank canister filters are frequently employed solely for mechanical filtering during routine tank cleaning and maintenance. They're also one of the most straightforward ways to deal with excessive copepod and amphipod larval blooms. Those little white bugs you frequently see swimming or crawling around in your aquarium?

For Chemical Filtration

If an aquarist needs assistance with a water quality issue, he or she can use granular (GAC) in the media chamber to help eliminate odors, medications, or other contaminants in the water, as well as other types of absorbing products designed to remove nitrates, phosphates, silicates, and other unwanted chemical elements or compounds. Filtering fresh tap water before using it to manufacture sea salt mixtures or adding it to an aquarium as top-off water is another example of this form of filtration.

For Biological Filtration

Even while many canister filters are built for and many aquarists use them that way, they're not the greatest choice for as a "primary" source. They may be adequate for smaller systems, but most do not have a large enough chamber to retain enough bio-media for bigger ones. As a result, they are insufficient for use exclusively for this purpose; however, one can be used in conjunction with another type of biological filter, such as living rock or a wet/dry trickling filter, to provide extra mechanical filtering of aquarium water.

Now, one of the most crucial aspects to consider when buying a canister filter is the water flow rate, not what the manufacturer claims, but what you'll obtain after taking into account a few other factors.

Water Flow Rate Considerations

The flow rate specified by the manufacturer is represented by an empty filter with no head pressure (the canister is not having to pump water uphill). The flow rate of a canister filter is affected by two primary components.

  1. Using extra media (carbon, etc.) or filter materials (poly filters or floss, micro pleat cartridges, sponges, etc.) inside the media chamber of the canister.
  2. Canister filters are often stored underneath an aquarium so there is a lot of head pressure to deal with, and possibly a long distance hose the water has to travel through. For the hang-on-tank type canister filter, you will get a water flow rate closer to what the manufacturer states because there is little or no head pressure to contend with.

Taking the above two parameters into account, you may determine the actual water flow rate after purchasing a canister filter and installing it in your aquarium, or you can get an approximation by using the flow rate equation to calculate GPH water flow rates before purchasing one. If you're still unsure whether your option is good after obtaining your estimate and considering the other variables, it doesn't harm to buy a larger filter than you think you'll need. You can never turn the water in your tank too many times, but you can have an issue with not turning it over enough, which can lead to poor water quality. A tank water turnover time of six to ten times per hour is suggested.

Other Feature Considerations

There are several different to select from. Eheim, Fluval, and Magnum, to mention a few, are some of the most popular classic canisters. Every manufacturer has its own specific design qualities, therefore performing your study on the many varieties is crucial. Some have unique features, such as those that employ powder or diatomaceous earth to ratchet up the filtration to extremely fine levels. According to Robert Fenner, these filters are classed as "pressurized filters," which might raise your power cost, thus they should be used only sometimes rather than continuously.

The best way to figure out what kind of canister filter you need is to determine what function you want it to accomplish, then decide from there which kind you should buy.

Another factor that can contribute to a canister filter not running at top efficiency and slow the water flow rate is ignoring proper or regular cleaning of the unit.

Here are some maintenance tips that will help prevent or lessen the further diminishing of a canister filter's water flow rate and operating efficiency.

  • Place your canister filter in an easy to get to spot for cleaning. If you don't, maintenance will be neglected because it's a hassle to service the unit.
  • If the manufacturer of the canister filter offers any useful tools for making the task of cleaning the unit a faster, easier, and drier one, in all likelihood the more often you will do it.
  • Purchase extra micron-pleat cartridges, floss, sponges, granular  (GAC), and other filtering materials or absorbing products to be used in the canister. By doing so you can quickly change or rotate the material in minutes, eliminating the hassle of having to remove and clean or rejuvenate the only medium you have on hand before you can place it back into the filter.
  • You will notice a slow down in your water flow rate when the filtration material in the canister becomes dirty. You can never clean or change it too often unless of course, you are using the canister for biological filtration purposes. If not, the filtering media or material should be cleaned or changed regularly, at least once a week. If left dirty this will decrease your water flow rate, as well as allow for the accumulation of an unwanted waste load on your system, which in turn contributes to poor water quality problems, the number one being an excess build-up of nitrates the aquarium.
  • Because algae, calcium, and salt crystal buildup can occur inside the hoses, canister chamber, impeller, and other areas of the unit where water passes through, at least once a month the filter should be taken completely apart and all sections cleaned to remove any possible blockages.
  • Don't be concerned about losing any biological bacteria from cleaning or changing your filter material. Remember, the purpose of a basic canister filter is to remove and clean your tank water of waste and debris. It's not a biological filter, unless of course for some reason you are using it for that purpose.

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