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7 Best Filters For 20-Gallon Aquariums – 2023 Reviews & Top Picks

Lindsey Stanton Profile Picture

By Lindsey Stanton


When it comes to keeping an aquarium in your home, whether full of fish or just plants, it requires maintenance and constant upkeep. Of course, one of the things that you will always need to have is a good aquarium filter. Without a good filter, the aquarium water will become dirty, smelly, discolored, and full of substances that can kill fish and plants alike.

Therefore, you need a filter without question. Today we are talking about 20-gallon tanks specifically, so we are here to help you find the best filter for a 20-gallon aquarium (this is our top pick). Let’s not waste any more time and get right to it!

wave tropical dividerA Quick Comparison of Our Favorites (2023 Update)

Rating Image Product Details
Best Overall
Fluval C Power Filter Fluval C Power Filter
  • Extremely high flow rate for its size
  • Flow rate can be turn up or down
  • Very easy to mount and install
  • Best Value
    Second place
    AquaClear Power Filter AquaClear Power Filter
  • Quick and easy maintenance
  • Easy to replace filter media
  • All 3 types of filtration
  • Premium Choice
    Third place
    Marineland Penguin Power Filter Marineland Penguin Power Filter
  • 100 GPH flow rate
  • Quick maintenance
  • Saves space
  • Marina Power Filter Marina Power Filter
  • Very easy to maintain and install
  • Energy-efficient
  • Adjustable flow rate
  • Tetra Whisper EX Silent Filter Tetra Whisper EX Silent Filter
  • Easy to set up
  • maintain
  • and install
  • Fairly efficient
  • Easy to change filter media
  • The 7 Best Filters For 20-Gallon Aquariums

    In our opinion, the seven below options are all top contenders for 20-gallon tanks. Yes, they are different, but they also work in their own right. Let’s take a closer look at them all right now.

    1. Fluval C Power Filter – Best Overall

    Fluval C Power Filter


    Our personal opinion is that this is probably the best 20 gallon aquarium filter out there at this time (you can check the current price at Amazon here). There are several reasons for this. However, the number one reason is because it engages in 5-stage filtration, something which not many other filters do. The first two stages engage in mechanical filtration, the third stage is a chemical filter, and the last two stages are biological in nature.

    In other words, you will hard pressed to find a filter that gets rid of more water impurities than this one. The filter cartridges are fairly easy to replace, which is always nice, plus the filter tells you when the foam pads need to be washed too.

    The Fluval C Power Filter is more than ideal for any 20 gallon aquarium. It can easily handle up to 119 gallons per hour. In other words, if you have a 20-gallon tank, this filter can clean all of the water in it up to 6 times per hour, or close to that anyway. At the same time, the filter flow rate is totally adjustable, which is nice if you have fish that don’t like strong currents.

    The really cool part here is that the trickle filter included in the mix works to filter the water much better when the flow rate is turned down. In other words, turning down the flow rate does not mean that less filtration is happening with the Fluval C Power Filter.

    The Fluval C Power Filter is a hang on the back filter, something we can always appreciate. Simply put, it does not require shelf space and it barely takes up room inside of the aquarium. Having an effective filter that doesn’t take up too much space is something that we always look out for.

    The fact that you can simply clip this filter right onto the back of your aquarium is really convenient no doubt. It might not be the biggest filter, but it works well, is easy to maintain, and easy to mount as well.

    • Extremely high flow rate for its size
    • Flow rate can be turn up or down
    • Has an awesome re-filtration system for low flow rates
    • Media is fairly long lasting and easy to replace
    • Very easy to mount and install
    • Extremely efficient at its job
    • Awesome five stage filtration for super clean water
    • Very loud
    • Not ideal for anything over 20 or 25 gallons

    2. AquaClear Power Filter – Best Value

    AquaClear Hagen Power Filter

    This filter is definitely more than ideal for a 20-gallon tank. In fact, this particular model can be used for any tank from 5 gallons to 20 gallons. What is really impressive about this particular aquarium filter is that it can process the entire contents of a 20-gallon tank up to seven times per hour, or in other words, it can process 140 gallons of water per hour.

    For such a small filter, this is very impressive no doubt. The flow rate of this filter is adjustable, which is always nice. However, the really cool part here is the re-filtration system. This means that when you turn the flow rate down, this filter works even harder to clean the water it is taking in.

    The fact that this is a hang-on-back filter is something that we always like. Sure, other filters work fine, but hang on back filters are always very space-friendly. They do not take up any space at all. Having them hang on the rim of the aquarium means that the inside of the tank is reserved for fish and plants instead of a filtration unit.

    On that same note, simply place the AquaClear Power Filter on the rim of your aquarium and tighten the clamps for mounting. It really does not get any easier than that. The whole filter is fairly solid and is definitely not going to leak, but when you need to get to the inside of it, it can easily open for quick maintenance.

    One of the things about this filter that we like is that the water stays in contact with the filter for quite some time. This translates to maximum efficiency and minimal energy usage. Having a low operating cost is something that we can all appreciate. When it comes to the filtration itself, this filter is able to engage in all three major types of filtration for super clean water day in and day out.

    It comes with AquaClear Foam, Activated Carbon, BioMax, and Cycle Guard for ultimate chemical, biological, and mechanical filtration. All in all, while this is a simple filter, it gets the job done without question.

    • Easy to mount and install
    • Quick and easy maintenance
    • Easy to replace filter media
    • All three types of filtration
    • Awesome flow rate of 140 gallons per hour
    • Flow rate is adjustable
    • Awesome re-filtration system
    • Does not take up much space inside of the tank
    • Can get fairly noisy
    • Motor is not of the highest quality

    3. Marineland Penguin Power Filter – Premium Choice

    Marineland Bio-Wheel Power Filter

    The next filter that we would recommend looking at is this Marineland Penguin Power Filter. First off, this particular model is designed to work for anything up to a 20-gallon tank and over a 5-gallon tank.

    This power filter features a 100-gallon per hour flow rate, so it can effectively process the water in a 20-gallon tank up to five times per hour. The result is water that is about as clean and clear as it is ever going to get. This filter comes with a mid-level tube intake which helps to improve water circulation

    To be honest, the Marineland Penguin Power Filter is nothing fancy, but it definitely gets the job done. It comes with patented 3-stage filtration, which includes mechanical, biological, and chemical filtration. Filter media is incorporated into convenient little cartridges, which makes maintenance a breeze.

    The cartridges come with the filter, so you do not have to buy them separately. The two-piece vented cover helps to ensure that this filter does not heat up, plus it makes changing the media about as easy as can be. Also, the filter media that comes included is of a fairly high quality for some really effective and efficient water filtration.

    When it comes to mounting and installation, the Marineland Penguin Power Filter more or less clips over the back of your aquarium. It literally takes 2 minutes to put everything together and get this filter mounted on your aquarium. The fact that this is a hang-on back filter is convenient too. It takes up minimal space both in and out of the aquarium, plus it is fairly energy efficient too.

    This thing is easy to set up, easy to install, and easy to maintain, all big benefits in our eyes. All in all, the Marineland Penguin Power Filter is definitely a really nice option to consider.

    • Media is included
    • Media is easy to change
    • Engages in all three major types of filtration
    • 100 GPH flow rate
    • Easy to mount and install
    • Quick maintenance
    • Has features to prevent overheating
    • Saves space
    • Can be a little noisy
    • Motor could be better
    • Needs manual priming

    4. Marina Power Filter

    Marina Power-Filter

    This is definitely one of the more unique-looking filters on this list. This filter is completely see-through. Some people don’t like this, but personally, we like the fact that you can see the inside of this filter at all times. This makes it easy to know when the filter media needs replacing, it makes it easy to see if something is broken or clogged, and we just think that it looks really cool either way.

    The Marina Power Filter is a hang-on-back model power filter, something we always like. Yes, canister and internal filters are fine, but they take up a lot of space in their own right, either inside or outside of the tank. However, the Marina Power Filter is designed to be sleek and compact, thus saving space. Heck, it does not take up any space inside of the tank at all, which is something that your fish definitely like.

    When it comes to maintenance, this thing is also quite easy to deal with. Being able to see the inside really helps here, but getting to the inside is just as simple. Speaking of easy, the Marina Power Filter is a self-priming filter, which is always a feature that we appreciate. Something else that we can really appreciate is that this particular filter is extremely quiet. Nobody likes a noisy filter, a problem which you thankfully do not have to deal with when it comes to this filter.

    The Marina Power Filter is ideal for tanks up to 20 gallons and it has a fairly good flow rate. Now, the flow rate for the Marina Power Filter is not as high as some of the other options on this list, but it can still process the entirety of a 20-gallon tank up to three times per hour.

    This is not amazing, but it is also not bad by any means. We do like how the Marina Power Filter has an adjustable flow rate so we can accommodate our fish as needed. When it comes to filter media, there is enough room for four different cartridges here, which means that it has the ability to engage in all three major types of filtration through four stages.

    • Very easy to maintain and install
    • See-through, a cool feature
    • Easy to hang on the back
    • Does not take up room inside of the aquarium
    • Room for four filter media cartridges
    • Fairly quiet
    • Energy-efficient
    • Adjustable flow rate
    • Does not need priming at all
    • Durability is questionable
    • May begin to vibrate with prolonged use

    5. Tetra Whisper EX Silent Multi-Stage Power Filter

    Tetra Whisper EX 45

    One of the best features of the Tetra Whisper EX Silent Multi-Stage Power Filter is the fact that it is ready to go right out of the box. You do not need to put any pieces together nor do you need to prime it. Yes, this thing comes fully assembled and is self-priming too. This thing has been built with simplicity and ease of use in mind, something which we can definitely appreciate.

    Literally, every single last thing about this filter is easy. To get it going, simply place it over the rim of your aquarium, secure it in place with the included equipment, and you are ready to go.

    Even better is the fact that this is a hang-on-back filter with great filtration capacity, yet it does not take up very much space at all. Hang-on-back filters are always really convenient due to the fact that they take up barely any space inside and outside of the tank.

    Something else that is pretty cool about this filter is that it works to maximize the level of water agitation and oxygenation, but things which are quite important no doubt. Of course, this thing is designed to be very quiet, something that you and your fish can appreciate no doubt.

    The Tetra Whisper EX Silent Multi-Stage Power Filter is designed to handle anything up to 30 gallons and it has a flow rate of 160 gallons per hour. In other words, even for a 30-gallon tank, it can process all of the water in the tank over five times per hour. This means that the water in your aquarium should always be clean and clear.

    This is a 3-stage filtration system, which means that it engages in mechanical, biological, and chemical filtration to remove all kinds of water impurities. What is also neat is that you get special time strips that let you know when the filter media needs replacement.

    • The ultimate in simplicity
    • Easy to set up, maintain, and install
    • HOB, saves space
    • Fairly efficient
    • Engages in all three types of filtration
    • Easy to change filter media
    • Very high flow rate, adjustable
    • Lets you know when media needs changing
    • Fairly quiet and energy efficient
    • Casing is not of the best quality
    • Motor might not last all that long

    6. Aqueon QuietFlow PRO Power Filter

    Aqueon Aquarium Power Filter

    Here we have a nice little hang-on back filter, one that doesn’t take up much space, has decent processing power, can be used for both freshwater and saltwater aquariums, and has some other neat features too.

    Space & Size

    One of the benefits that you get with this particular filter is that it does not take up space inside of the aquarium.

    This is a hang on back filter, so it does need a few inches of clearance behind your tank, but it won’t eat up valuable real estate inside of the tank, and that is something we can really appreciate.

    Media Types & Stages

    This is a pretty decent three-stage filter for smaller tanks. It comes complete with easy change cartridges, which is a big bonus as far as we are concerned.

    In other words, instead of having to replace media separately, all media is housed inside of a special cartridge. Yes, this thing does have three stages of filtration, which include mechanical, biological, and chemical filtration.

    What is also nice here is that there is a little filter change indicator included, so you know when the filter media needs to be replaced. It’s not the most powerful option out there, but should do fine for tanks that are not too heavily stocked.

    Processing Power

    The Aqueon QuietFlow PRO Power Filter has the ability to process anywhere from 60 to 80 gallons of water per hour, so many times the amount of water in a 20-gallon tank, which should be more than enough, even for a fairly heavily stocked aquarium.

    • Takes up no space within the tank
    • Easy change filter cartridges
    • Super easy to install and maintain
    • Fine for medium-stocked tanks
    • Not the most durable
    • Requires a decent amount of rear clearance

    7. Penn Plax 455 Cascade Corner Filter

    Penn-Plax Cascade Corner Filter

    This is a cool little submersible filter to go with, one that fits neatly into the corner of an aquarium.

    It’s got great processing power, lots of filter media, and a few other features you might also appreciate.

    Space & Size

    Now, this is a submersible filter, so it does need to be directly in the tank, so automatically, it does take up a bit of space.

    However, this is a corner filter, which is actually pretty rare, but also quite useful, because comparatively, it will take up less space than a filter that is not placed in a corner.

    It’s only a couple of inches deep and wide, so either way, it’s pretty small and space-friendly. What is really cool about the Penn Plax 455 Cascade Corner Filter is that, if you want, you can actually place it horizontally.

    Media Types & Stages

    This filtration unit does come with three stages of filtration, and yes, this includes all three types as well.

    This is a combination mechanical, biological, and chemical filter for aquariums. Now, here you do have to replace media separately.

    It’s not just a small cartridge, but the upside here is that you can choose what type of media and how much of each type of media to put inside of it.

    This kind of versatility is quite beneficial as far as we are concerned.

    Processing Power

    What is really impressive about the Penn Plax 455 Cascade Corner Filter is that it can process up to 120 gallons of water per hour, which is way more than enough for a small 20-gallon tank.

    It’s about twice as powerful as it needs to be and can definitely handle some really heavily stocked aquariums.

    • Amazing water processing rate
    • All 3 types of media
    • Easy to maintain
    • Doesn’t take up too much space inside the tank
    • Can be mounted horizontally
    • Has a tendency to clog

    tropical fish 1 dividerWhat Type of Filter Should I get For My 20-Gallon Tank?

    There are of course different types of filtration units out there for aquariums. A 20-gallon filter can come in various forms or types, so you might be wondering which one is best for your tank.

    Let’s take a quick look at some types of 20-gallon fish tank filters, the 3 main ones.

    aquarium with coral, clay pot, cichlids, plants
    Image: Frantisek Czanner, Shutterstock


    The first kind you can get is a submersible filter for aquariums. These tend to be fairly easy to set up and to maintain, although you may have to remove certain components for cleaning or to replace media.

    These tend to be fairly inexpensive, and they work well enough, although they usually don’t have the most amazing processing power of all filter types.

    You can find small ones that can easily fit into most aquariums but do keep in mind that these go right in the water, so they will take up space either way.

    Generally speaking, these are not too expensive and they will work fine for an average tank that doesn’t have too many fish.


    The next kind of filter you can go with for your 20-gallon tank is a canister filter. These things are much more powerful than any other kind of filter for aquariums out there, but of course, they are also much more expensive.

    These tend to be fairly easy to set up, not too difficult at all, although maintaining them can be a bit of a pain. In terms of space used, on one hand, they are external filters, so they don’t take up room inside of the tank, but larger ones will need lots of shelf space.

    Canister filters are quite impressive because they can hold a ton of media and media types, and can usually process an insane amount of water per hour.

    A canister filter taken apart showing the insides and workings


    Some would say that the best 20-gallon fish tank filter is a HOB or hang-on-back filter. These tend to be mid-level in terms of, well, more or less everything.

    They tend to have decent processing power, decent room for media, they have an OK level of durability, and generally don’t cost too much either.

    Many people like them for smaller tanks because they hang on the side or back of the aquarium, so they don’t take up space inside of the tank.

    wave tropical dividerConclusion

    At the end of the day, there are obviously way more than 5 options in terms of fish tank filters. However, for 20-gallon tanks we personally feel these 5 are some of the best (the Fluval C4 is our top pick). Take a closer look at them if you are on the hunt for a new filtration unit.

    Feature Image Credit: Open Mind Art, Shutterstock

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