Most people would tell you that canister filters are far superior to internal filters and then proceed to list benefits, such as; canister filters do not take up space inside the aquarium, canister filters have more space for media and canisters have higher flow rates, among other benefits. However, I am inclined to disagree with these people. Although the benefits of canisters, as listed above, are legitimate enough, they are no reason to discredit internal filters.
A major concern for a lot of fish keepers when it comes to filtration is how much space is taken up by equipment inside the aquarium. Those interested in presenting a clean, aesthetically pleasing aquarium tend to pay the most attention to the amount of equipment inside the aquarium, as filters and heaters can ruin the aesthetic quality of an aquarium. However, that does not translate into; equipment inside an aquarium equals an ugly aquarium. Different people maintain aquariums for different reasons, which is why setting yourself clear goals for your aquarium hobby is essential in order to achieve the aims you set for yourself. If maintaining an eye-catching display aquarium is your goal, then canister filters may very well be your best option. However, if you’re more of a purist and keep fish for the sake of keeping fish, then there are many reasons why you might purchase an internal filter over a canister filter.
Canister filters are a lot more expensive than the average internal filter and can leave a significant dent in your bank account. Some people assume that the price of a filter is a reflection of the quality of the filter. However, this is not true. Although it may be true that purchasing a well-known brand of filter goes towards ensuring that the filter will perform as promised, we all know that the big brands can be overrated.
Avid supporters of canister filters often sight the increased media capacity as a major reason as to why canister filter represent the best form of filtration for freshwater setups. However, there is a small flaw in the logic of this argument, as increased media capacity does not equal increased filtration efficiency. In other words; it shouldn’t be a case of quantity over quality. Many canisters filters have internal designs that may contribute to media inefficiency. One way of determining the efficiency of a canister filter is to examine to positions of the intake and outlet pipes. Filter designs which have the intake and outlet pipes positioned opposite one another on the motor compartment of the canister represent some of the most inefficient designs. Designs such as this result in most of the water flowing through a restricted portion of the media, resulting in only some of the media operating at maximum capacity. Aquarists would do well to remember that the bacteria that convert toxic compounds into harmless ones require high levels of oxygen to operate efficiently. In practice, that means that the media in the high-flow areas will likely be the media doing the most work.
The exception to the observation that I have made above in relation to the positions of intake and outlet pipes applies to filters which have ridiculously high flow rates. High flow rates does not refer to the amount of water being pushed around the aquarium, rather the amount of water flowing through the filter, often measured in litres per hour. The difference is that filters with high flow rates produce varying amounts of flow in the aquarium, depending on the size of the outlet pipe. Wider pipes reduce water pressure and thus, reduce flow in the aquarium and vice versa. Filters which match the above description may be able to deliver sufficient oxygen to all areas of the media by sheer power alone.
Higher Flow Rates
Higher flow rates are arguably one the benefits of canisters filters that cannot be denied. Most canister filters have flow rates far above the capabilities of most internal filters. However, there are a few, such as the Otto Internal Power filter, that can match the flow rates of canister filters. The Otto internal is by far the best filter I have ever used. Although sponge is the only media that this filter uses (although other media could be used if so desired) the high flow rates ensure that bacterial populations on the sponge are operating at maximum capacity.
When it comes to arguing whether cleaning an internal filter is easier than cleaning a canister it can be argued either way and is largely dependent on the individual filter being used. The benefit of canisters is that they need to be cleaned less often than do internals, however, in order to do a full clean, it takes more work to clean a canister. Those canisters that have a ‘back-wash’ feature, which involves using one of the filter’s outlets to move water through the filter and out into a drain etc. would require less frequent maintenance, however, the need for maintenance is not eliminated altogether. Although internal filters should be cleaned at least every two weeks, the cleaning process is quite simple and should take less than ten minutes. However, there is one other downside to internal filters. A heavily clogged internal filter may release some detritus open switching off the filter, as the suction is no longer able to hold the detritus in the media. However, this is easily mitigated by scheduling a water change at the same time as filter maintenance. The detritus usually drops directly underneath the filter and can easily be vacuumed up afterwards.