Aquarium Filters
First we need to briefly discus the main types of aquarium filtration and what they do for our aquarium and inhabitants.
Mechanical
Simply stated, mechanical filtration is the use of any type of material such as filter wool/floss, sponges, micron cartridges, etc., that traps suspended debris that is in the water column.
Of this material; pore, weave, density, etc. determine how small a debris particle can be trapped.
As well it is worthy of note that generally speaking any mechanical filter material that traps smaller particles is also going to clog up and need to be changed or cleaned sooner. So filtering water in layers starting with coarse to fine will help prevent this problem and allow longer amounts of time between cleaning as well as prevent filter back up or even over flow in the case of many HOB filters.
Biological
Biological filtration is the process that generally utilizes a media that makes for an oxygen rich surface for aerobic nitrifying bacterial to colonize. This bacteria will remove highly toxic ammonia, then nitrites, then finally leaving as low toxicity nitrates. THIS PROCESS IS THE MOST IMPORTANT ASPECT OF AQUARIUM FILTRATION according to many long time and experience aquarium experts.
Conversely, a media that allows for de-nitrifying bacteria to colonize in a near zero oxygen environment (anaerobic) colonize will reduce nitrates.
Some examples of common biological filter material/media include sponges [which can vary greatly in how many bacteria that can colonize a given square centimeter], volcanic rock, ceramic media, bio balls, aquarium substrate, and products such as AAP Matrix.
For anaerobic de-nitrifying filter material, we need to use material that is dense enough that allows water and bacteria to penetrate, but most oxygen is used up by aerobic nitrifying bacteria before getting deep inside the material.
The before mentioned volcanic rock and AAP Matrix along with a few other products and deep sand beds can sometimes accomplish this. Be careful though with deep and fine sand beds, as this can often propagate sulfur fixing bacteria that produce hydrogen sulfides.
Further Reading:
#Hydrogen Sulfide Production in Aquariums
#Fish Beginner; Nitrogen Cycle Basics
Our Recommended Product Resources:
Chemical
Chemical filtration involves the adsorption and/or absorption of chemical toxins from the aquarium water. These products often do not absorb or adsorb ammonia, nitrites, or nitrates. Compounds that yellow the water, aquarium medications and treatments, alcohols, airborne insecticides, are just a few of the compounds and/or toxins that may be removed by various chemical filter medias.
Examples include activated carbon, AAP Purigen, AAP Phosbond, zeolite and many more.
Further Reading:
#Activated Carbon for Aquarium or Pond Use; Information, Use Table
Our Recommended Product Resources:
#Seachem Phosbond from AAP
Germicidal
Germicidal Filtration generally describes the use of true UV-C Sterilization, as opposed to UV Clarification commonly employed by most UV products now sold on the market for under $60.
This may also include the use of Ozone when coupled with a Protein Skimmer, but this is a marine filter device that will not work well in freshwater aquariums.
Further Reading:
#Fish Beginner; Aquarium UV Sterilizer Use
#UV Sterilization; In Depth Information
Further Reading about Filter Material/Media in general with more in depth information: #Aquarium & Pond Filter Media, Material; Mechanical, Bio, Chemical
Now let's discuss the different aquarium filter types and their benefits with types of filtration in mind!
As each filter type is described including their strength and weaknesses, consider too that the best filter for an aquarium generally involves more than one filter, so that one achieves redundancy should a problem occur and as well this often combines the best of each and improves generally the most important aspect of aquarium filtration; biological filtration.
Hang on the Back or "HOB" Aquarium Power Filer
These filters which have changed much over the decades are still a simple mainstay for aquarium filtration.
Most now employ an over flow method of returning water to the aquarium with a pump either in a small well/sump inside the filter or in the intake just under the water level of the aquarium.
With this over flow in mind, it is important that filter material does not get so clogged with debris, that water instead of flowing out the front back into your aquarium, instead flows out the back onto your floor.
The use of pre-fitted cartridges is the mainstay of most of these filters. These cartridges provide both mechanical and chemical filtration [using carbon inside the cartridge].
However one popular HOB filter, the AquaClear as well as the newer more premium AAP Tidal HOB Filter uses foam and carbon inserts. This can sometimes allow for more versatility and often very good bio filtration assuming the foam insert is not thrown away. In fact these are the best choice if bio filtration capacity is what you need most in your HOB filter.
Of the two, the more modern and higher quality, higher quality AAP Tidal filter is definitely the better choice over the AquaClear.
But, this filter design generally does not do as a good a job trapping fine debris from the aquarium water column [some aquarium professionals have also reported a higher percentage of impeller issues with the Aqua Clear over other brands].
Beware of the really cheap stripped down HOB filters sold at Walmart and many discounters as these generally only have a cartridge and at best a small insert to allow for colonization of nitrifying bacteria. What happens is each time you throw out the cartridge, you throw away much of your nitrifying bacteria and thus destroy the ability of the filter to remove toxic ammonia and nitrites WHICH IS ITS MOST IMPORTANT JOB!
This does not mean there are not good economy filters that perform the three primary aspects of aquarium filtration, most notably biological filtration.
AAP/SunSun makes and excellent and reliable economy Hang on the Back Filter in the HOB-501 and HOB-702 that provides reasonably good biological filtration [or at least as good as most comparable sized HOB filters].
An AAP model 702 dual outlet HOB power filter was graciously given to me by an aquarium pro for my 40 gallon the replace my Whisper, and boy does this filter rock! While this filter make cost less than the Whisper, Hagen and other brand names, it easily outperformed these others I have used of similar size!!
Other HOB filters of note include the Marineland Pengiun, the Whisper, the Rena Smart & Super Clean HOB power filters, among many others.
Further Reading, including HOB filter troubleshooting [a subjective article, but still an excellent read if only for the troubleshooting section]:
#Aquarium Filtration; HOB Power Filters
Our Recommended Product Resources:
#AAP/SunSun High Bio Capacity Economy HOB Filters [Models 501 & 702]
Sponge Filters
Sponge Filter are often less known, yet these have been around for quite some time now. Still prized by breeders and those demanding simplicity along with high bio filtration performance.
There is also a wide range in performance between the many imports and the patented USA made sponge filters that are available in both fine particulate filtration and reticulated sponges for high flow.
These filters do not generally come with a "power source", rather these utilize a separate air pump which uses an up-flow of air to pull water through the filter material or a power head water pump attached to the top of the filter exhaust tube/port so as to move water through the filter material.
The best of these filters such as the AAP Hydro Sponge Filter #5 and #5 PRO have capacities that rival the largest HOB Filters such as the Aqua Clear 110. These are also available in combo filters so as to combine the best of fine and coarse mechanical filtration.
These are probably one of the best beginner filters while being a top notch filter for advanced aquarium keepers as well. The best such as the AAP Hydro Sponge have bio capacities per filter size that are only beaten by Fluidized Sand Bed Filters, generally far exceeding most any HOB filter often for far less $$ as well.
These can also be relatively good mechanical filters depending upon the size of the filter and the sponge material [which the better versions are patented and not readily available at discounters]. Just beware of the many patent violating knock offs out of China [under many brand names such as "Aquarium Cop-op"] that still have utilize inferior sponge material
One other somewhat less common use for sponge filters is as a "pre-filter" that attaches to the intake of a HOB or Canister filter. These prevent intake of fish fry and keep the "parent" canister or HOB filter from clogging as quickly with debris.
More importantly the better sponge pre-filters such as the patented AAP "Filter Max", will improve bio filtration and prevent crashes of nitrifying bacteria when the parent filter is cleaned.
Further Reading:
Our Recommended Product Resources:
#AAP Sponge Pre-Filters for Attaching to HOB or Canister Filters
Canister Filters
The versatile canister filter is a popular, generally large capacity aquarium filter that performs mechanical, chemical, and biological filter well. Some canister filter such as the SunSun have a UV function as well, however these UVs are ALL 100% clarifying UVs, NOT level 1 sterilization capable, despite what some less than honest retailer might tell you.
In fact many sold at eBay and Amazon along with other discounters come with medium pressure UV bulbs that are barely clarification capable, so do not base your purchase decision on whether a canister filter has this feature or not, only look at it as a mild bonus feature. I would also caution eBay buyers that those sold here do not come with the added filter media and upgrades that make the filter more durable [as well I would remind readers that purchasing via eBay or Amazon does not support the aquarium hobby, as articles such as this get no support from discounters who also provide little to no knowledge based customer support]
Back to the pros and cons, these filters are excellent for larger aquariums where high capacity filtration is needed. As well these filters when set up optimally with lava rock, AAP Matrix, or similar bio media can be excellent bio filters. However if not set up properly and not serviced when due, these can also be nitrate factories.
One other negative is these filters can be messy to change and often can be a difficult filter filter for many beginners, especially if one is not as "handy". If you count yourself as such a person, I would suggest avoiding these filters and going with a sponge or HOB filter instead.
Besides the before mentioned Canister Filter upgrades by AAP, other popular models include the Eheim, Fluval, and the professional choice the Filstar.
Further Reading, including canister filter troubleshooting [a subjective article, but still an excellent read if only for the troubleshooting section]:
#Aquarium Filtration; Canister Filters
Some Aquarium Canister Filter Resources:
Fluidized Sand Bed Filters
Although less known by many aquarium keepers, in part because these filters are not commonly sold by popular discounters, the Fluidized Sand Bed (or FSB) Filter is one that should not be over looked by an aquarium keeper looking for a filter with the highest bio capacity per liter of space of ANY other filter!
There are no negatives with this filter when it comes to bio filtration as these are the kings of bio filtrations, despite those who are unfamiliar and continue to think wet/dry or canister filters are the better choice. The simple truth is most true aquarium professionals are very familiar with this filter for just the reason of bio filtration.
The negatives of this filter is that these filters perform no chemical filtration [assuming it is needed], and perform little to no mechanical filtration.
Good mechanical filtration by another filter BEFORE it enters the FSB Filter is a MUST for this filter to work efficiently. If set up correctly with a pre-filtered power head/water pump or canister filters running it, a FSB can be a trouble free and awesome addition to most any high bio load aquarium. If not set up correctly, these can also be more problematic.
For this reason I would term the FSB Filter more of an intermediate aquarium keeper and above filter, not a beginner filter [for a beginner looking for high bio capacity, look to a good sponge filter such as the AAP Hydro Sponge].
If one does decide a Fluidized Sand Bed Filter is for you, consider using AAP NPX BioPlastics inside along with AAP Purigen in another filter to also keep nitrates in check [unless a planted aquarium]. We also suggest the 3rd generation AAP/TMC V2 FSB Filters over the older generation FSB Filters still commonly sold.
Further Reading:
#Aquarium Filtration; FSB Filters, including FSB filter troubleshooting
#Aquarium Fluidized Bed Filter Review
Our Recommended Product Resource:
Wet/Dry Filters
This is a filter style that has now been around for quite some time. This was based in part from sewage treatment plants whereby the technology was adapted for aquarium use.
The problem is, and I know this is controversial, these down sized versions simply do not perform as well for what we need in our aquarium environments. For one, when configured with bio balls as with the popular Eshoppes Wet/Dry filters, these actually have far less bio capacity than a canister filter running with AAP Matrix or Volcanic rock when a liter per liter comparison is made.
As well these filters are proven nitrate factories, since bio balls cannot perform ANY bio de-nitrification at all. I have been told by aquarium professionals that they have many inquiries as to how to control runaway nitrates with wet/dry filters, in particular the Eshoppes style. Often the best solution is to simply remove the filter rather than purchasing much more expensive equipment in a "dog chasing its tail" type of response to a filter that should never have been purchased/used in the first place.
For planted freshwater aquariums, the nitrate issue may not be so much a problem for fish aquariums or especially marine reef aquariums, but then there is the aspect that these filters also quickly scrub CO2 from the aquarium, which is a problem for CO2 loving plants.
The bottom line is while there are those who might disagree, we at Fish Beginner stand by these statements that are backed up by long time aquarium professionals consulted for this article. The best decision for most common wet/dry filters is simply do NOT purchase [there are some designs that work well, but many of these are DIY]!
Further Reading: