The debate is on. Which is the best? Which is the worst? Why do we use different types of filters for different types of fish? What filter is best for my specific tank setup? In this post we will discuss the three main filtration types. What are the pros and cons to each? What is best for a specific tank setup? The areas covered will be mostly for freshwater tanks as saltwater tanks use a more complex system of filtration often including sumps and overflows that a normal freshwater tank would not include.
So first what are the most common types of filtration? The most uncommon and sometimes considered obsolete form of tank filtration is the under gravel filter system. The second is probably the most common type of filtration system used in general aquariums today, the hang on back or power filter. The final type of commonly used filter would be the canister filter, which mostly are used with larger tanks but some prefer to use them on all tanks.
The under gravel filtration system usually consists of a system of one or two plates that are rigged and are set under the gravel when first setting up the tank. The corners of the plate/plates have predrilled holes in them big enough to fit a piece of clear or colored piping on it that will run vertically up the tank and connect into power heads. The power heads suck water through them at their rated speed and create a siphon in the gravel pulling all suspended material down into the gravel. The pros of an under gravel system are that suspended particles are usually pulled down into the gravel keeping the overall tank appearance very clean and free of debris. That is about the only pro with the system. The disadvantages highly out number the advantages. The disadvantage to these systems are they are virtually impossible to run with sand or any fine particle substrate as it will end up being sucked through the plate and into the power heads. Another disadvantage is that the gravel commonly does not hold enough bacteria to sustain a full cycle and keep the decomposing waste and food particles from creating higher levels of ammonia and nitrites. The gravel needs to be vacuumed on a very rigorous schedule to completely remove the debris left behind since it is always pulled into the gravel. The biggest disadvantage to under gravel filtration is there is virtually no media choice available.
The hang on the back or power filter is the most common filter used for recreational aquarists as it is widely accessible, cheap and come in many different variations. The most common quality hobs include Aquaclear, Tetra Whisper, and Marineland Emperor and Penguin series filters. There are other options available like Top Fin, Aqua Tech, and various other brands but these often include less media options than the higher quality hobs. HOB filter pull water from an intake tube that is user adjustable with attachments. The water is pulled up the intake by a propeller and sent into the filtration hold in the filters. Different hobs have different filter media options. The Aquaclear series has more media options than other hob filers. Its mechanical filtration stage is a sponge, then a carbon bag or most prefer just loading it with biomax (ceramic rings). If you have ammonia problems you can also load the aquaclears with ammonia remover bags as media. Whisper and Marineland filters usually have less media capacity and include pre-made carbon filters. However, biobags can be purchased and stuffed with whatever filter media the user prefers. The cheap price, numerous filter media options, and low energy use make the hobs the most commonly used filtration system. The only real disadvantage to hobs is in a planted tank scenario where little water flow on the surface is required to keep needed CO2 in the water.
The final filter option would be canister filters. Canister filters are often used on larger tanks and by aquarists who have a general preference for them. They are external filters and generally set beside or under the tank and are used commonly in aquariums that are meant to be viewed from both sides. The sleek intake and return tubes allow for the front and back to be viewed where a hob would block the view from either side. Canisters pull water through an intake and into the canister. Once in the canister the water is filtered in a 3 stage process as the hob. First stage is mechanical filtration which is usually a sponge or some type of fiber material. The second stage is the chemical stage which generally would include carbon or for most ceramic rings. The third stage is the alternate chemical stage and again would be ceramic rings, biomax or some even use a high polishing fiber to keep the water crystal clear. The advantages to a canister filter are external filtration so no visual blocks on the tank, they are generally larger than hobs so they can carry way more filter media allowing for more bacteria development on the media and decreasing the risk of recycles, and last they allow attachments of spraybars which allow controlled movement of water streams by the user. The only real disadvantage to canisters is the initial cost of the unit.
As for overall performance the canister may be a higher stability filter but if you have adequate filtration on your tank with hobs you should not be able to tell the difference. The best bang for their buck will be the hob as the cost for a high performance hob that filters around 100 gallons would be $60. For a canister that will filter 100 gallons general price range will be $150-$200. At the end of the day it is user preference and what has worked the best for them though. Hopefully this will help out a little.