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Welcome my Aquariawise family!
It is time, at last, to talk about aquarium filters.
And the truth is this. There are so many different types and brands out there, it’s quite easy to get confused and buy something you do not want or even need, especially if you are new at fish keeping.
Overall, the most common types, and what most people know, are the sponge, hang-on-back, canister, internal, and under-gravel filters.
But there are others like power, box, trickle filters, and some unique units like protein skimmers, fluidized bed filter, and UV filters, that not many aquarists have come across or even heard of.
For that reason, this post will explore aquarium filter in detail to help you understand and determine what unit is best for your aquarium.
But lets first look at “What filters do in fish tanks”, and “Aquarium filtration methods: What are the three types of filtration?"
What Do Filters Do in Aquariums
The main purpose of aquarium filters is to remove waste and dirt from your water column and maintain a healthy environment for your fish and plants to thrive.
A filter will remove both organic and inorganic waste, albeit using different filter-media for each type of filtrations.
Usually, the waste that accumulates in your tank, and needs expelling, results from fish excrements in the form of ammonia, and dirt from uneaten food, dead plants, algae, substrate residue, decor dirt, mineral deposit in water and more.
That said, it is imperative to note that you need different filter media for solid, biological, and chemical waste, and that is where the three types of aquarium filtrations come in.
What are The Three Types of Aquarium Filtration
Depending on the type of dirt you want to remove from your fish tank, you will either need a biological filtration, mechanical filtration, or chemical filtrations.
But this does not mean you will require three different filters, it only means having different filter-media to target specific elements.
Biological Aquarium Filtration
Arguably, biological filtration is the most important of all.
It is tasked with removing waste from the water column in the form of ammonia and nitrites, which would otherwise poison and kill your fish.
The ammonia develops in the tank when your fish excrete their waste into the water, though other organic dirt sources such as leftover food, and decomposing plants and dead fish create ammonia spikes as well.
How your filter works to help remove this waste is through healthy bacteria that develop in the bio-media inside your filtration system.
The gram-negative bacteria (Nitrosomonas and Nitrobacter) first breakdown ammonia into nitrites and then to nitrates, which are less harmful to fish unless in high concentration.
Given this background, you will need some form of bio-filter media in your filtration system to expel biological waste from your fish tank; please note bio-filtration is a must for your fish to remain alive.
Mechanical Aquarium Filtration
The mechanical filtration system in a fish tank trap waste particles such as uneaten food, fish waste, algae, substrate dirt, and plant debris floating in the water.
But unalike to bio-filter media that trap soluble waste, mechanical filters only trap solid waste that is yet to or does not decompose.
As such, mechanical filtration is the first stage in the filter process, meaning the media should sit in such a way that the water coming in the filter hits it first.
That said, bear in mind most mechanical media also promotes the development of beneficial bacteria, especially in the case of sponges and pads, and aid in biological filtration, albeit scantily.
There are different types of mechanical filtration media, that mostly depend on filter types, but most units use sponges, pads, or packs of wool with openings that vary in size; from coarse to fine.
Some mechanical filtration systems such as power filters employ cartridge media.
Chemical Aquarium Filtration
The third aquarium filtration method, which is chemical, removes dissolved particles that are not ammonia via activated carbon, resins, and other absorbents.
Chemical filtration media is not used as much as bio and mechanical media but can be quite useful in some situations. For instance, when using tap water from a source with a lot of dissolved elements such as copper and chlorine.
Please note that while chemical filtration is not a must, I highly recommend adding a chemical-media in your filter because although most soluble elements won’t kill your fish, they will affect their development and all-around well being.
Aquarium Filter Types
Now that you have an idea of what aquarium filters do, and the different filtration methods that are necessary for a healthy fish tank environment, let’s look at different fish tanks filters, and how each compares to the other.
Below is a quick-scan list of aquarium filters types. Please note the list may not be exhaustive, but it does capture most of them.
- Sponge filters
- Internal filters
- Hang on back (Power) Filters
- Canister filters
- Under gravel filters
- Corner (Box) filters
- Surface skimmers
- Protein skimmers
- Diatomic filters
- Fluidized bed filters (Aquarium reactor)
- Wet/Dry (Trickle or Sump) filters
- UV sterilizer filter
You will notice that some types are quite similar, with the differences are almost negligible.
The only glaring differences you will note, and which are most likely to influence your decision are:
- Placement in or on the tank: Internal vs external
- Filter media used: sponge, pads or cartridge
- Mode of operations; working mechanism
- Size and design
- Effective use or purpose
#1 — Sponge Filters
Sponge filters are arguably the most basic and easy use; they have no complicated part.
You can disassemble a sponge filter effortlessly, clean and set it up in the tank with little to no prior knowledge on aquarium filter use.
As you would expect, sponge filters are ideal for use in small starter aquariums, nano, breeding, and fry growing tanks. It is also the only filter that will not suck-in your fish babies from the water column.
If you decide to use this type of aquarium filter in a large fish tank, you may need to couple it with another, more powerful unit, or go for more than one sponge filter. But that does not mean a sponge filter will not work as the primary filtration unit; it will function faultlessly!
Sponge filters are so named because they use a sponge as the main dirt-trap (media).
How a Sponge Filter Works
A sponge filter is a simple device that filters your water via a sponge media.
The process starts with the powered sponge filter air pump or power-head creating suction that makes water go through the sponge which removes solid waste and ammonia from the tank.
Basically, the system works the same way a regular hang-on filter operates.
Even so, it is crucial to note that for a sponge filter to clean your water, beneficial bacteria need to first colonize the cleaning media (sponge). For that reason, you need to have it in the aquarium for at least one month before using it as the sole filtration-unit.
Of course, if both the filter and the tank are new, you will have to cycle your aquarium before adding your fish.
How To Set Up A Sponge Filters
Sponge filters are, in my humble opinion, a great addition to freshwater aquariums.
Here is how to set one up.
- Assuming your filter is new, hence not joined into one compact unit, just follow the instruction from the manufacturers and clip everything together. It’s pretty easy!
- Just make sure each part clips into place correctly. Otherwise, the middle part of the filter (with the sponge on it) will break, and you will have to replace it.
- Once the bottom and middle parts are clipped together, pass the airline tube through the larger plastic tube and connect it to the intake (bottom-middle part combo).
- Clip the plastic tube in place on the intake, and you just set up a sponge filter.
Best Place (Tank) To Use a Sponge Filter
Sponge filters are quite expandable and can be used in a host of tank sizes and for various purposes. But they function better in some situation than others.
Use a sponge filter in:
- Breeding tank
- Fry growing aquarium
- Quarantine tank
- Hospital tank
- Nano aquariums
- Shrimp tanks
- Small fish tanks (between 5 and 20 gallons)
#2 — Internal Aquarium Filters
An internal aquarium filters, like the sponge-filter, is another type of filtration unit used in the hobby quite a lot.
The reason the filter is called internal is because the unit goes inside the fish tank (submersible), as opposed to sitting outside the tank, then connected through a pipe for the water to circulate.
Internal filters usually come with suction cups at the back used to attach the unit on to the tank and keep steady in place.
By design, most filters of this type are simple with just a handful of primary components. They include a plastic pocket with the sponge inside, and a small water pump attached on top of it.
You will also see two nozzles near the tops of the unit. One for clean water flowing from the filter, and another one that attaches to a small pipe that serves as the airline.
At the very top part of the filter, you’ll also get a cable with which you connect the filtration unit to the power source.
Most people attach their internal filter units in one corner of the fish tank via suctions cups, but you can also put them at the aquarium base, especially if you need more agitation at the bottom.
There are several advantages of using this type of filters, but mostly, it’s because of their availability and low cost. For a pretty small-price, you will get a piece of equipment that will both clean your water and aerate your tank.
Moreover, internal filter rarely clog, though they can be cumbersome to clean when they do become dirty because you must take them out of the aquarium.
How an Internal Aquarium Filter Works
When an internal filter is running, water is sucked in at the bottom of the bottom through slits on the container that holds the filtration media.
Once the water gets to the sponge inside, beneficial bacteria break down the ammonia into nitrites and the nitrates, then the water goes up and is released back into the tank via the outlet nozzle on the air pump compartment.
In smaller internal filter systems, the sponge serves both as the biological and mechanical filter, trapping solid waste as well as ammonia. But in bigger units with larger media containers, there is room for three media types for all filtrations stages.
As for the airline tubing at the top, you can choose to leave it inside the aquarium, or outside the tank when you require extra water aeration.
Internal aquarium filters come in many different sizes, meaning you can use them in small, medium and big aquariums, just make sure you purchase a unit rated for two to three times your aquarium capacity.
#3 — Hang on Back Filters
Hang on back filters are another common type of aquarium filtration system, that is easy to use, and ideal for beginners and experienced aquarists alike.
They vary from your average sponge and internal filters, in that they do not go inside the tank, but rather suspend on the tank’s back, hence the name.
Hang-on-back filter can be used on most standard home aquariums and will perform all three filtration stages (types) without a problem. However, you do not want to use them in fry or shrimp tank because the fishes often get stuck in the siphon.
Quite often, power HOB filters come with fish tanks if you purchase a ‘complete’ kit from the store.
They use a standard floss or foam as the mechanical filter media and activated carbon for chemical filtration. But you do not need a stand-alone bio-filter means as healthy bacteria that develop in the filter cartridge mostly get the job done.
Even so, advanced units will have extra space for you to include additional filtration media if you like, plus some even incorporate a bio-wheel to allow more area for bacteria to colonize.
How Hang On Back Filters Work
A hang-on-back filter is placed at the top edge of the aquarium and pulls water from the tank through a hose into the filtration unit.
A pump inside the filter is what powers the unit to pull the water from the aquarium.
In the period the water will be inside the filtration system, it will go through several filter media, depending on how many you have, and trickle back into the tank clean and safe for fish to live in.
Overall, hang-on-back filters provide adequate surface agitation and clean the tank satisfactorily. However, this comes with a strong current, which is not ideal for some fish and inverts.
Best Aquariums For Hang On Back Filters
As I mentioned above, power filters are ideal for most standard aquariums, but there are a few where these units are not very well placed.
Ideally, use a hang-on-back filter when you have strong swimmers that do not mind a strong current. Also, make sure the fishes are big enough not to get sucked into the system as water flows in for filtration.
I prefer not to use HOB power filters in tanks with shrimp, fry, or slow swimmers like betta, angelfish, and discus. Instead, I apply them in aquariums that have active fish like tetras, danios, and platys that love to ride the wave or bottom dweller like cories that rarely come to the top, but still require enough oxygen at the base of the tank.
#4 — Canister Aquarium Filters
Canister filters are debatably the most reliable filtration systems in the hobby, both for keepers with freshwater and marine tanks. They are also more efficient for use in planted aquariums.
Same as power filters, they sit outside the tank, though not hanging at the back like HOBs.
That said, canister filters are a little more complicated and involve more energy to set up and maintain than the other three filter types (sponge, power, and internal).
While canister filters, you would need to take them apart, drain, clean, and put them back together, all this while making sure not to disturb the healthy bacteria in the setup.
The process needs to be quick and meticulous, as such, canister filter units are not ideal for beginners.
Also, the initial cost of a canister filter is quite high, the more reason they are best used by experienced fish keepers with tones of skills and larger tanks.
How Canister Aquarium Filters Work
As you would expect, canisters filters are a little more complicated to put together than sponge, internal, and power filters, more so, because of the extra intricate components involved.
Even so, the general workings of these filters are almost the same as other units, with the end game being to draw the water from the tank, filter it, then drain it back while clean and safe for fish to live in.
In a few words, canister filters have tubes that go into the tank. The outflow hose draws water into a filter chamber where it is taken through several filter media to remove impurities.
Once the water has gone through all levels of filtration in the chamber, it then flows back into the aquarium via a spray bar powered by a pump.
The air pump can either be integrated into the unit, usually built into the cover or base, or separate sitting outside the canister system.
Depending on the unit you have, the direction of flow can either be top-bottom, bottom-top, back-front, outside-in, or center-out. Also, the stages of filtration will differ with the unit, but I highly recommend getting one that has all three (biological, mechanical, and chemical) media.
One advantage that canister filters have over HOBs is less water splash, meaning less water is lost. The same goes for losing fish because canister systems do not require an open-top tank to function.
Best Aquariums For Canister Filters
- Saltwater aquariums
- Large freshwater tanks
- Planted aquariums
- Heavily stocked fish tanks
- Reef tanks as an complimentaly biological filter
- Turtle tanks
#5 — Undergravel Filters
As the name suggests, undergravel filters are primarily biological filtration systems that sit under the substrate in an aquarium, though the powering mechanism (air pump) is usually placed outside the tank.
The part that sits inside the tank is really just a plastic plate that covers the bottom of an aquarium to provide an ample area for beneficial bacteria to establish.
While the design of undergravel filter plates may differ between brands, they all have holes in them and operate under the same principle.
The best place to use this type of aquarium filters is when you need extra surface agitation inside your tank or to form nitrifying bacteria colonies at the base of your aquarium.
However, undergravel filters can be quite unreliable when gravel compact, and the remaining holes filled with solid waste particles, which reduce the flow of oxygen past the bacteria.
For that reason, you may want to have another filter in your fish tank to filter mechanical (solid) waste from the water and keep anaerobic pockets from forming in the substrate; cleaning your gravel regularly also goes a long way.
Having said that, undergravel filters might serve as mechanical filters, albeit ineffectively, but they cannot operate as chemical filters. So, you may also want to add a separate chemical-filtration-media in your tank.
How Undergravel Filters Work
The undergravel plate under the substrate has lift tubes located on each corner, which extends to the top of the tank. Through the pipes, air-stones draw water at the bottom along with bubbles, or a small power-head (pump) draws it from the top.
The water goes through the gravel, where nitrifying bacteria use oxygen (from water) to breakdown ammonia and nitrite into the less harmful nitrates, cleaning and making your aquarium habitable.
Where to Use Undergravel Filters
Overall, undergravel filters can work in a host of aquarium setups, but many aquarists do not use them a lot these days, because they tend to pull all the dirt in the tank on to the gravel, making you do a lot of substrate maintenance.
The filter also predominantly grow nitrifying bacteria, which make them only useful as bio-filter media, whereas other units like canister and HOBs filters will sort out all your filtration needs with a single kit.
There is also the argument on undergravel filter limiting plant growth because they inject too much oxygen in the substrate, which is not ideal.
#5 — Corner (Box) Filters
Corner or box filter are the old boys of the aquarium filtrations world, but they still have some unique application in the hobby. They work as effectively as hang-on-back units, and even carry some unmatched pros over the newer types.
Notably, corner filters are a good alternative for tanks with slow-moving aquatic animals like betta fish, axolotl, angelfish, gouramis, and frogs.
They also are cheap and long-lived and will keep functioning unless they are dropped and cracked. You will also love having a corner filter in your tank in time of a power outage because they can operate even on battery-powered air pumps.
Even so, the oldies do have a few cons, including their limited use. As a rule of thumb, you can only use corner filters in a small fish tank that’s between five (5) and ten (10) gallons in size.
You also need to make sure the fishes you have in your aquarium do not have a large bioload, unless you are willing to do some extra cleaning and water changes.
How Corner (Box) Filters Work
Like most other types, corner filters are air driven. They have a long, narrow tube that creates suction at the bottom, which then pulls water through the filter media.
The water enters the chamber through slots on the filter’s lid, then pass through the media in the middle, and exit the unit from below.
With box filters, you are not limited on the filter media choice, they allow you to add anything from a coarse, medium, to fine sponge as long as it lets water go through it.
Corners box filter will serve most of your basic filtration needs resulting in water that is both chemically and visibly clean.
Where to Use Corner Filters
I already mentioned that corner filters are ideal for slow-moving aquatic life, but you can only use them in smaller fish tanks.
So, if you have beginner nano tanks with just one or two fishes like betta or gouramis, then a corner filter would be an ideal choice.
However, any tank with fish that produce a lot of waste like goldfish, will not be effectively clean when using a box filter.
Please note that from here on, we are done with the most common aquarium filters, especially those used in freshwater tanks. The remaining systems are mainly used for specific applications, away from the three principal filtration methods (biological, mechanical, chemical).
#5 — Surface Skimmers
Surface skimmers are special use filters that are mainly meant to reduce oily films and scum from the surface of fish tank water, which if left in there can impede light transmission and reduce gas exchange
They, in turn, contribute to the decrease of microorganisms, better overall oxygen exchange, and greater light penetration.
Add a surface skimmer to your fish tank if you notice unsightly films in the water surface such as fat, proteins, and waste matter, which can feed harmful microorganisms and gradually affect your fish.
Oily films and scum in aquariums are mainly derived from nutrients and proteins that rest on the water surface. Many fish foods add to this problem due to the ingredients in their recipes, and it can look unsightly if not dealt with regularly — Aqua-fish.net.
A surface skimmer will also help keep your water clear and pristine for longer.
That said, there are many different types of surface skimmers, each designed with a specific role in mind. You will get some that are only meant for larger aquariums, and others that go directly into a canister filter system.
For this reason, I highly recommend you do some research before you purchase this filter to make sure it is compatible with your aquariums. Purchase a separate surface skimmer when you have a small fish tank filter that cannot house a skimmer in the pipework.
How Surface Skimmers Work
Stand alone surface skimmers are just placed in the tank with suction cups in such a way that the top of the equipment lines with the surface of the water in the tank.
The kits are powered independently by a separate motor, which sucks the water to remove oily debris. Usually, the inlet where the water goes in will have a toothed fringe to keep debris out of the filtration system.
If a surface skimmer is incorporated into a canister or HOB filter pipework, it is usually hooked up to the inlet hose.
Regardless of the skimmer you have, all types suck in water from the top and bottom of the system. The top-skimmer-part then remove all oily crap and surface-scum by running the water through a filter media.
Overall, surface skimmers don’t cost a lot, you only need to make sure you get a unit that is compatible with your filtration system; canister or hang-on-back.
#6 — Protein Skimmers
Protein skimmers (foam fractionators) are another type of supplementary filter device that targets specific dirt and scum in aquariums and are mainly used in saltwater and reef tanks.
Protein skimmers mode of operations is pretty close to that of surface-skimmers, but contrary to common belief, they do not serve the same purpose in fish tanks.
While surface skimmers only remove surface scum, protein skimmers remove organic dirt like protein from the whole water column, allowing the primary filtration unit to perform more efficiently.
Protein skimmers are so named because they mainly remove proteins from the fish tank, but the general term of all organic dirt expelled by these kits is called skimmate.
How Protein Skimmers Work
Protein skimmers come in many different designs, but the principles of how they work largely remain the same. In brief, they produce air bubbles which trap dirt from the water.
The two most common types available in the market and what is used by hobbies are the hang-on-back and sump versions. Even so, the design of each unit varies and may include co-current, counter-current, venturi style, and ETS plans.
Different manufacturers also put unique twists on their product for brand identity and what have you.
How Protein Skimmers Clean Aquarium Water
I’ve mentioned, the principle of operations of all skimmers remains the same regardless of the design. As such, the explanation below will help you with whichever unit you have.
Protein skimmers mix large volumes of water with small air particles which attract organic waste in the tank including protein and collect on the bubble surface.
The waste then raise gradually to the upper water column along with the bubbles and rest at the surface in as foam.
The foam (skimmates) is then pushed up the neck of the skimmer and collect in a collection cup or waste line to be discharged. get more insight here
Best Aquariums to Use Protein Skimmers
Protein skimmers are an excellent choice for saltwater and reef aquariums, but not so much in freshwater tanks.
The reason skimmers are not as ideal for tropical tanks is that freshwater water lacks the ability to foam air bubbles which are essential to the operation of protein skimmers.
In marine tanks, they remove organic waste, oil films, and other yellowing agents that would otherwise impede light penetration, reduce oxygen distribution, and impact on your fishes health.
They also help maintain low nitrate levels in reef tanks where low settings are crucial for coral health.
What’s The Difference Between The Protein and Surface Skimmers
Apart from a protein skimmers being a little more intricate than surface skimmers, they are also more effective at removing organic waste in aquarium water.
Surface skimmers only remove oily scum and organic waste from the water surface, but protein skimmer units will remove dirt throughout the tank by diffused aeration.
Even so, while the two filtration systems are not the same, they do complement each other when used together, and will both help the primary filter keep your aquarium clean and healthy for aquatic life.
#6 — Diatom Aquarium Filters
Diatom filters are special filtration kits used for polishing water to almost perfect clarity. They are designed to mechanically filter the tiniest aquarium dirt and scum.
Using diatom filters is advised when keeping fish such as discus that like things on the pristine side, though they are not recommended for everyday use.
These filters also come in hardy for owners with tanks plagued by green algae.
As you would expect, diatomic filters are so named because they use Diatomaceous Earth powder as the filter media. The powder loaded into the unit is fine creating small pores that trap tiny dirt particles in the water.
How Diatomic Aquarium Filters Work
We’ve said that diatom filters use diatomaceous earth to trap tiny dirt and scum in fish tanks.
But what is diatomaceous earth (also called diatomite)?
Diatomite is a collection of small empty shells from diatoms that collect in sediments at the bottom of water bodies. The carapaces result when the single-celled organisms (diatoms) die and are full of minute pores that trap dirt in tanks.
Basically, most diatom filters work on a vortex system where water is pumped into a chamber that is filled with the earth, usually along with carbon to trap any toxins that are released when the debris is filtered out.
#7 — Fluidized Bed Filters
Fluidized bed filters are hang-on-back or canister type filters that offer superior biological filtrations by moving aquarium water through a mass of small granules, usually silica.
Their mode of operations is more akin to undergravel filters, but the designs mostly resemble that of canister and HOB power filter units.
The cylinder type can stand in your sump, on the floor or under your tank, then connected to an air pump which sucks water from the tank and through the filter system.
Please note that fluidized bed filters can be referred to by any of these other names.
- Suspended particulate filter
- Suspended sand filter
- Phosphate reactor
- Media reactor
- Aquarium reactor
- Phosban reactor
- CO2 reactor
- Biopellet reactor
- Carbon reactor
- Chemical reactor
How Fluidized Bed Filters Work
Fluidized bed filters provide biological filtration very similar to that of undergravel units, where nitrifying bacteria grow on the surface of sand in the bed and process ammonia and nitrites as the water pass through.
Fluidized bed filters look more like canister or HOB filters but work more like undergravel filtration units. They process ammonia by passing water through a sand bed with tons of nitrifying bacteria that process ammonia and nitrites.
The water needs to be pumped into the filter system by an air pump, which does not come with the unit. As such you may need to budget for an air pump to run your fluidized-bed-filter.
The power-head should go in the fish tank and connected to the filter via a tubing system, but it can also sit in a sump if you have one for all your filter units.
Basically, the water gets into the fluidized bed filter from the bottom, through the silica or whichever media, and come out at the top clean and safe enough to put back into the aquarium.
#8 — Wet/Dry Trickle (Sump) Filter
Wet/dry trickle filters are mostly used in saltwater and reef tanks, but they can be quite useful in freshwater tanks as well.
Their designs vary, but the most common types are built in a sump tank because the only essential components are a trickle system and a large surface area for bacteria to colonize.
Because most fish keepers prefer to build their wet/dry trickle filters in a sump system, it’s not uncommon for the units to be called sump-filters.
I suggest you look at this article by love fish tank for better insight on wet/dry trickle filter configurations, and how they work.
#9 — UV Sterilizer Filters
UV sterilizers are designed to solely kill disease-causing organisms because regardless of how clean your water looks, there always are a few pathogens lurking in there.
While ordinary aquarium filters suck in water into the system and put it back in the tank visibly cleaner, microorganism still survive, only UV filters will completely eliminate them.
UV sterilizers come in various sizes and shapes, and most sit on the side of an aquarium and can go into any tank with enough space; tropical, saltwater, and reef setups alike.
Use these sterilizers to kill organisms like bacteria, viruses, and parasites before they can infect your fish.
A UV-filter will also eliminate microalgae, though you need to remove their residue with frequent water changes rest you water changes its color.
How UV Sterilizers Work in Aquariums
The general working of UV filters do not differ a lot from other filtration systems, the just draw water the ordinary way, clean it and release it back into the aquarium.
However, instead of the usual sponge filter, the water is pumped through a crystal sleeve and passes a high-intensity UV-light that exposes harmful organisms to lethal levels of radiation and kill them.
The device usually covered in an opaque canister to stop the ultraviolet rays from reaching the rest of the fish tank.
What is The Best Filter Type For Your Fish Tank
No one aquarium filter will serve all the filtration needs of a fish tank. As such, it’s better to consider what best serves your immediate need then upgrade as you get better at the hobby.
That said, the type of fish tank you have will at times dictate the kind of filter you’ll use. An ideal filtration system for a tropical aquarium will not necessarily work as expected in a saltwater or reef tank.
Moreover, while units such as sponge filters will work best in quarantine tanks, HOBs might be better when you need more surface agitation and undergravel system best when looking for more aeration at the bottom of your aquarium.
Therefore, I recommend you consider your setup as a unique ecosystem different from any other.
Below is a quick look at the different freshwater aquarium configurations and their appropriate filter types for each.
Freshwater (Tropical) Fish Tanks
Sponge filters, one of the most basic forms of aquarium filtration are surprisingly also one of the best to use in freshwater aquariums, especially for beginners.
The filters are pretty popular and have been used by a ton of fish keepers for a long time, as such, their track record is tested and proven. The units are also quite cheap compared to other types and for the same level of reliability.
The main advantage of having a sponge filter is their ease of use and are easy to pull apart, clean, and change the media.
They also do not have a lot of power, so your unit will not push your fish or move them around in a current. If you have a fish that is a slow swimmer, you will especially like this feature.
The second type you should consider for your tropical tank is a HOB (power) filter.
These filters are suited for freshwater tanks that are a little bigger, but they do have some downsides.
They tend to be powerful than sponge filters, which is ok if you have a big tank because you need your water surface to be moving for aeration.
Another advantage about HOB filters is they are pretty easy to clean, plus you can replace the filter pad without having to open anything up.
On the downside, they tend to be more expensive than sponge filters, more so when you want a quality unit. The cheaper ones tend to overflow, something you do not want to happen.
Hang-on-back filters are also not aesthetically pleasing since they ride on the fish tank, meaning you will always have an odd-looking thing on the side of your aquarium.
Luckily, the other best type (in my opinion) to use in tropical tanks will make all the cons of HOBs units go away; that is canister filters.
Canister filters are the surest bet when you have a large tropical tank that is either overstocked or with fishes with a big bioload. They are ideal for aquariums that are 40-gallons and upwards.
They are also best for display aquarium where you do not want a box hanging on the walls or sitting in a corner inside your fish tank.
Even so, canister filters are pretty powerful, so you want to only use them in larger tanks. They are also harder to pull apart and clean hence not ideal for beginners.
On average, it takes about an hour or two to clean a canister filter.
It’s ok if you decide to implement two systems in your tropical tank to make sure your aquarium is well cleaned and have a back-up for use while cleaning either of your units.
As for specific use aquarium filters, the only system I would probably recommend for freshwater tanks is a surface skimmer to remove oily and organic scum from the water surface.
Internal filters, undergravel filters, and corner filter will also clean your tropical tank effectively, but I do not consider them the best. Of course, they have unique pros, but also cons.
Breeding, Quaratine, and Hospital Tanks
A classic requirement of any breeding tank, quarantine or hospital tank is slow water current that does not disturb your fry or sick fish.
You also need a unit that won’t suck in your fry, but still provide enough filtration and aeration inside the aquarium.
As such, the go-to filter type for these kinds of tanks is a sponge filter.
You will barely have any unnecessary movement but with superior biological filtration that can even handle several sick fishes where need be.
That said, I do not recommend using a HOB power filter in either of these three setups, for very ‘water-movement’ reasons.
Thats all for this article, but I’ll do a couple of follow up posts, for the best units of each filter system discussed here (the most common ones at least), so be on the lookout.
Enjoy the hobby.