Aquarium filtration is arguably the most important aspect of keeping healthy fish. Two main factors impact what you choose as the best canister filter for the gallon capacity of your fish tank. Namely, the fish you keep and the GPH potential of the new pump.
In this guide, I’ll make filter recommendations for both large and small freshwater aquariums, based on flow rate data and livestock. What are the best and most reliable canister filters for a 125-gallon fish tank then? What if the tank held 75 or even 55 gallons of water? Water volume plays a big role in your decision.
Calculating the needed flow rate of aquarium canister filters
To determine the needed flow rate of your new aquarium filter you’ll need to take into account the type of aquarium livestock in combination with the fish tank’s size.
1. GPH potential gets reduced with filter media
GPH stands for Gallons Per Hour and signifies the hourly water circulation an aquarium filter can maintain. This metric is strictly related to the maximum fish tank size a canister filter can handle.
Now, when I first researched canister filters I noticed that most manufacturers did their own evaluations of how large an aquarium tank their products could filter.
However, upon further reading, I found out that these estimations are based on tests where the filter has no media inside and the water tank has nothing but a bare bottom.
For this reason, I recommend that you ignore the “for aquariums of up to ** Gallons” labels and multiply the provided GPH data instead.
When doing the calculation you should look for a turnover rate of no less than 5 times the total water volume in your aquarium. If you’re going for a densely stocked fish tank, however, you will likely want to increase that number to 7 or 8 times per hour.
An exception to the rule is large heavily planted tanks with a few schooling fish in them.
The latter would possibly need a total water circulation of between 4 and 5 times per hour.
By following these guidelines you will make sure that your aquarium water remains crystal clear at all times.
I made a chart that will help you determine the exact GPH rate needed for your aquarium (bookmark this page for further reference).
Take a look at the filter flow rates required for each fish tank size:
|Aquarium Size:||Recommended Filter Flow Rate:|
|125-gallon or larger tank||no less than 625 GPH|
|100 or 90 gallon tank||at least 450 to 500 GPH|
|75-gallon tank||a minimum of 375 GPH|
|100 to 90 gallon tank||at least 320 to 400 GPH|
|55-gallon tank||around 275 GPH|
|30 gallon tank||no less than 150 GPH|
|20-gallon tank||over 100 GPH|
These are the recommended flow rate minimums for each aquarium size.
It should be noted that the more media a canister filter can hold the better it is at preventing deadly ammonia spikes in the aquarium water.
2. Determine the type of your livestock and its density
The larger the fish you keep, the more waste they will produce. Waste is dangerous because it can quickly turn into ammonia which is highly toxic to fish.
There are some aquatic inhabitants that are messier than others of their size.
Some messy aquarium livestock includes:
- Large carnivorous fish such as Oscars, most South American Cichlids, Arowanas, Stingrays
- Large herbivorous fish such as some African Cichlids, Goldfish, and Plecos
- Freshwater eels
- Aquatic turtles
What is the Best Canister Filter for the Gallon Capacity of Your Fish Tank?
Have a quick look at this chart showing the canister filters that best match each aquarium size:
|Canister Filter Name:||For Freshwater Aquarium:||Price Bracket:|
|1. Penn Plax Cascade Canister Filter||30, 40, 55 and 75-gallon fish tanks||$$|
|2. Eheim Classic 22(XX) External Filter||10, 15, 20, 30 breeder, 40 breeder, 50 and 55-gallon fish tanks||$$|
|3. SunSun HW External Canister Filter||40, 55 and sometimes 75-gallon fish tanks||$|
|4. Fluval (X)07 Aquarium Canister Filter||20, 30, 40, 50 and up to 55-gallon fish tanks with the latter being planted||$$$|
|5. Fluval FX(X) Series Canister Filter||75, 90, 100 and even understocked 125-gallon fish tanks with plants||$$$$|
|6. Aqueon QuietFlow 400 Canister Filter||55, 75, 90 and up to 100-gallon fish tanks that are planted||$|
Below I’ll recommend a particular piece of gear for every possible setup, according to my experience and observations.
For optimal recommendations, I am considering fish tank sizes, livestock, and aquascape, combined with the pros and cons of the particular canister filters. You can also check my detailed reviews for each model I mention. I have personally used or know real-life examples of people who’ve had success with all of these products.
Here are the best canister filters for the gallon capacity of your fish tank:
1. Optimum Canister Filters for 125-Gallon or Larger Fish Tanks
In a 125-gallon fish tank, the filter is the most important piece of gear along with the lighting fixtures. To best maintain a 125-gallon fish tank you can choose among these canister filters:
- Fluval FX6 Canister Filter – Use the FX6 as a primary filtration unit. Check the unit on Amazon.
- Penn Plax Cascade 1500 – To be used as a secondary filtration unit. Compare the this filter’s price at Chewy and Amazon.
There’s no easy way around this.
In my experience, to keep such a large freshwater fish tank realistically clean you’d need 2 separate canister filter units. The combined GPH rating of both should revolve around 1000 for a 125-gallon aquarium. For larger tanks – aim for a water circulation of 7 to 8 times, because filter media and stocking will hinder the advertised flow rate of your canister filters.
And now the big question – what aquarium filter combo should you use in a 125-gallon fish tank?
My success has been with combining one quality canister filter as the main source of water circulation and a cheaper one, to make up for the additional filtration.
Of course, the turnover rate also depends on your livestock. If you plan to have a large, heavily planted tank with just some cardinal tetras in it a single FX6 unit may suffice.
However, my guess is that you would like to have at least 3 medium to large-sized fish in such one tank.
Or maybe you’ll stock it with all the cichlids you could find. Or have some mean turtle(s) that will double in size in the next couple of months. Or, perhaps, a silly 30″ long freshwater eel.
All of which produce copious amounts of waste and need killer filtration to thrive.
On my 125-gallon tank that’s housing my huge Oscars, I run a Fluval FX6 + a Penn Plax Cascade 1500 Canister Filter (linking you to both on Amazon and Chewy in the bullet section above).
The FX6 has 560 GPH and the Penn Plax has 350 while both are bulky and provide enough bed for beneficial nitrifying bacteria.
The combined GPH of these two is a little over 900, which circulates the whole water volume of my aquarium more than 7 times per hour.
My water is as transparent as air and my ammonia and nitrite readings are solid zeroes.
If you’re lower on the budget you can replace the Cascade 1500 with, the way cheaper, SunSun which is half the price but still provides almost as strong filtration.
The SunSun HW-304B is listed as a canister filter capable of 525 GPH, however, it is not clear if that’s the pump output or the water circulation potential of the whole filter. In my observations, the real number leans towards 300 without any media.
Anyway, in the long run, the Cascade 1500 will be the most durable of the two, though it (too) has the appearance of a cheaper filter at first sight.
Mind that you get what you pay for.
They can go strong, but may occasionally break and should not be your permanent solution.
Investing in a high-end filter will save you tons of anxiety in the long run.
It’s how you should view it – as an investment.
It’s the reason why I got the FX6 and, perhaps, so should you WHEN you can afford it.
If you have the pocket for it, this canister filter is a no-brainer. The motor of the Fluval is among the best on the market right now. It is also quite long-lasting and the chance of breaking is rather insignificant.
Though a sole unit like the FX6 won’t be enough for a 125-gallon fish tank with my setup, it still handles a great portion of the filtration for me.
In my opinion, the FX6 is a must for an aquarium of this size, but you can get flexible with your second unit.
If you want to go full Fluval you can use their 407 Series (you can look that one up on Amazon) as your secondary filtration and benefit from its circulation potential of 245 US gallons per hour.
If you want to approach the matter in a frugal way you can buy a used 407 on Amazon and save at least half of the price. If you choose to walk that path, know that Amazon has a solid protection policy to ensure you get quality second-hand equipment.
It is German-quality gear that may last you for 10 years or more.
In my opinion, none of the aforementioned canister filters beats this one.
It moves tons of water but also has an enormous filter media capacity of 4.5 gallons, which, by the way, you can’t find elsewhere. With so much filter media the stability of the NItrogen cycle in your large aquarium is more or less guaranteed.
If you have a fish tank that’s over 150 gallons and you want to provide its inhabitants with the best possible filtration, the Eheim 2262 is for you.
For an aquarium that’s 200+ gallons, you may need a second unit to help the Eheim, with Fluval’s FX6 being a sound choice.
When it comes to filtering monster-sized fish tanks this Eheim canister filter stands undisputed, in my opinion.
2. Optimum Canister Filters for 90 and 100-Gallon Fish Tanks
- Fluval FX6 Canister Filter – If you only have space for a single aquarium filter. Check this canister filter on Amazon by clicking here.
- Polar Aurora 525 GPH – Get 2 of these filters as a budget alternative. Amazon.com has the Polar Aurora version and so does Chewy.
I’m guessing that if you plan to have a 90 to 100-gallon freshwater fish tank you’ll absolutely stock it with medium to large-sized fish. Its livestock will define what canister filter you should install, really.
If it’s that rare case where you just want a lightly-to-not planted 90-gallon aquarium with hundreds of small community fish in it, then, surely, a single Cascade 1500 will do the job. It’s a popular canister filter, that provides a strong flow rate of 350 GPH.
This will rotate the water in your 90-gallon community tank about 4 times per hour, which should be enough if it only houses small schooling fish such as neon tetras and zebra danios. The filter pad trays of the Cascade 1500 are not the largest out there, but they will be more than enough for such a setup.
However, this is often not the case.
For a 90-gallon fish tank that’s heavily stocked with cichlids or some other medium to large fish that produce a lot of organic waste, you’d need powerful filtration. The total volume of aquarium water should be circulated at least 6 times per hour, which means that you’d likely need a canister filter that has a flow rate of about 540 GPH.
Fluval FX6 (with a link above, to check this exact model on Amazon).
Really an astonishing canister filter with monstrous water turnover capacity.
It will circulate the water in your tank 5 to 6 times, depending on the filter media. Fluval’s FX6 external filter has an estimated GPH rate of 563 for total aquarium circulation, and a pump that has an output of 925 GPH (not the same thing).
My experience with the Fluval canister filters has been that they are reliable and work as described.
They’re very quiet, yet super powerful. I don’t really see any other filter suitable for a setup like this.
I don’t have 90-gallon, nor 100-gallon tanks at the moment, but, as I mentioned earlier, I run an FX6 on my predatory 125 gals in combination with another filter.
Anyway, I’m sure you did notice the price of the filter I’m recommending.
I can mumble all day how the numbers are justified, but I won’t bore you with that.
I reviewed the FX6 in my other article on the top canister filters and you can check that one out if you’d like (I left a link to it up in this post).
Essentially you get what you pay for, and this investment will probably last you no less than 5 years from my experience.
This filter can handle the waste of pretty much anyone – aquatic turtles, large fish, or both.
What I also like about it is that it has enormous space for filter media.
The Fluval FX6 is really one of the best and most reliable canister filters for larger aquariums on the market, right now.
In fact, it’s so powerful that occasionally it may suck up a baby fish or five. If you have that make sure you secure the intake pipe with a barrier of some sort. Or simply move them to a breeding tank.
I’m aware of how that sounds, but it’s not as bad as you may think.
The SunSun HW-304B (link to Amazon above, by the way) claims to turn over 500 gallons of water per hour. In my experience, this is not the truth, but it still realistically reaches around 300 GPH.
With 2, the total flow rate of your 90-gallon tank will be pushing 600 GPH, which is 6.6 times of hourly water turnover.
Now, look at its price.
That’s right, you can get two of these canister filters for less than the money you’d pay for a single FX6.
I can’t help to agree that for a tighter budget aquarium, the SunSun filters are absolutely killing the competition.
They do move around plenty of water and have 4 trays for filtration media, so there’s that.
With 2 of these, you will provide crystal clear water in a well-stocked 90-gallon aquarium. The SunSun HW-304B is the go-to choice for many frugal aquarists with larger fish tanks.
However, I think it’s important to mention that these filters won’t last you for 5 years, and if they do, there may be some repairs along the way.
Also, they come with a built-in UV sterilizer, which I don’t recommend turning on for more than a couple of hours on the weekend. The sterilizer will eat through the plastic if it stays on for longer than that.
You should get a separate UV aquarium sterilizer if you need one.
Anyway, the SunSun HW-304B canister filters are a pretty good choice for a fish tank of this size if you don’t currently have more money. However, If you do I would always recommend going for the rock-solid FX6.
A SunSun HW-304B will last you for at least a year and a half with proper maintenance.
My honest recommendation here is to let your current budget decide.
3. Optimum Canister Filters for 75-Gallon Fish Tanks
- Penn Plax Cascade 1500 Canister Filter – For 75 gals tanks with less than 80% bioload. See whether Chewy or Amazon have the best offer for the Cascade 1500 canister filter.
- Aqueon QuietFlow 400 – For a fully stocked aquarium. Check this unit out on Amazon.
- Fluval FX4 High Performance Aquarium Canister Filter – For a tank with heavy bioload. You can see the Fluval FX4 here.
According to my experience, to filter 75 gallons of water in a fish tank you’d need something that can turn the water at least 5 times per hour. If the aquarium you have is predatory and contains large fish or turtles that are carnivorous and therefore even messier, make that 6 to 7 times.
The Cascade 1500 (click the upper link to view the exact model on Chewy) would be perfect for most setups here. It is rated at 350 GPH which can be enough for a decent water circulation of 4.6 times per hour.
I recommend this filter if you are not stocking your freshwater 75-gallon fish tank to the fullest and also keep some aquarium plants inside.
I use the Cascade 1500 on my heavily planted 75-gallon aquarium that harbors small community fish.
I would say it’s moderately stocked, and I am positive it is close to 80% bioload. My readings of ammonia and nitrate are well close to 0, with ammonia being constantly there and nitrites ranging between 0 and 0.2 ppm.
When dealing with a planted tank, however, you’d want enough flow to move around carbon dioxide, without tearing your plants apart. It’s why I chose the 1500 series, and I am (still) pretty happy with my choice.
Anyway, with larger fish such as Oscars, cichlids or freshwater eels things can get dirty.
I’ve found that to actually filter the water here, you’d need a stronger unit.
My recommendation for a decently stocked 75-gallon fish tank would be the Aqueon QuietFlow 400. It is rated at a turnover of 400 gallons per hour, and I have to say, that may very well be the real number.
By the way, I only have one tank with Oscars currently yet, despite the messy creatures in it, I achieve crystal clear water.
And let me tell you, with an Oscar that’s 10 inches long the filter you have is probably the most important equipment in your aquarium system at that point.
If you risk it with a weaker aquarium filter you may end up killing your monster fish, causing ammonia poisoning in the water.
For a 75-gallon tank with a small turtle, or one that is FULLY stocked with cichlids I’d strongly recommend scaling your new canister filter up a little.
Price included, but not by much – around $60 when none of the items is on sale.
If that seems like a lot, let me tell you that these $60 can be the difference between wasting $$$ at having to buy a new filter soon after, and a healthy, year-long filtration.
An appropriate choice here would be the Fluval FX4 aquarium canister filter.
Aquatic turtles are as dirty as it gets, and if you’ve ever owned one you’d know that.
The FX4 model of Fluval’s canister filters is classified as a good choice for up to 250-gallon fish tanks, but this is not your concern.
What we’re looking at here is the GPH flow rate, which is 450, as advertised. This is likely enough to handle a 75-gallon tank with aquatic turtles as a turtle habitat needs a solid canister filter in place.
It also has multiple filter media trays, for you to stock with whatever pads you desire. This will suffice for even the messiest turtle and you won’t end up tearing your tank down, because of stagnant water issues.
4. Optimum Canister Filters for 55-Gallon Fish Tanks
- Polar Aurora Canister Filter – A budget aquarium filter. You can find the SunSun HW-304B at Amazon or at Chewy.
- Penn Plax Cascade 1500 – For heavily-stocked tanks. You can find this canister filter at both Chewy.com and Amazon.com.
- Fluval 407 External Canister Filter – For an understocked 55-gallon tank. Click here to see the Fluval 407 at Amazon.
For freshwater aquariums of this size, I’ve estimated that you’ll likely need a canister filter that spins between 240 and 330 GPH, depending on the bioload in the fish tank.
Bigger fish tend to be messier and if I was planning to keep such I’d want to be prepared.
I can recommend that you go after either the SunSun HW-304B or the Cascade 1500 canister filter. They both provide a flow rate of over 300 GPH which should be enough to handle the water circulation in a 55-gallon fish tank perfectly.
What’s the difference between the two you may ask?
When I’m getting a SunSun I know that it will come at a lower price and that I will get really powerful aquarium filtration for my bucks.
The Cascade 1500 canister filter is a little bit pricier, but it’s manufactured in the US and will run for 3 or more years upon good maintenance. It is also stronger on the flow rate than the SunSun with 350 GPH compared to around 300 for the latter.
Note that the SunSun claims to provide a flow rate of 525 GPH but I’ve found that to not be true. The realistic water turnover would be around 300 GPH with a margin of +\- 20.
Anyway, if you’d want to stock your 55-gallon aquarium heavily, the choice really depends on your budget.
Obviously, if you really can’t afford to spend the extra $ then go for the SunSun. By the time a change is needed (still, 1 to 2 years) you’d probably have enough money to get something durable.
However, if right now you have the budget for it – you should absolutely go for the Cascade 1500, as it is way worth it in the long run.
It’s simple – let your pocket decide.
Anyway, in case you plan to keep something very messy such as larger pleco fish, Oscars, a community of cichlids, or some freshwater eels I recommend stepping up your game, for obvious reasons.
When keeping medium-sized fish or turtles in your 55-gallon tank you should aim for ~350 gallons per hour of water turnover.
I ran such a fish tank just until recently (I expanded it) and I had a Cascade 1500 doing the filtration. This canister filter is top-notch and keeps my ammonia where it belongs – at 0.
I got mine because with these types of fish in my aquarium I could not compromise with the filtration.
But what canister filter would work best in a heavily planted 55-gallon tank with just a few schooling fish in it?
In my opinion, the Fluval 407 would be a suitable choice for this setup because it provides a flow rate of approximately 250 GPH.
With it, the effective water circulation of the aquarium sits at around 4.5 times, which is enough to move around the CO2 for your aquatic plants. This GPH rate will also have a smaller chance of sucking up the tinier fish or their fry.
The canister filter is a bit pricier itself but I am only trying to recommend units that do the best work for their price here.
The 407 would make sense for a 55-gallon freshwater planted tank with a lot of smaller schooling fish.
You can read my reviews about all of the units I mention in my article on the top-rated canister filters that I linked to, up in this article.
5. Optimum Canister Filters for 30 to 40-Gallon Fish Tanks
For 30 and 40-gallon freshwater fish tanks, a sound choice of an aquarium canister filter would be the Penn Plax Cascade 700 Series. The Cascade 700 is rated for an aquarium of up to 65 gallons and has a GPH of 185. This means that it will turn the water of your 30-gallon fish tank around 6 times per hour and over 4 times for a 40-gallon one.
Anyway, I consider the Cascade 700 strong enough to handle the filtration of a fully stocked 30-gallon aquarium.
However, if you’re not pushing it with the bioload, a simple Cascade 500 would do the job.
The Penn Plax Cascade 500 has a GPH of 115, which will turn the water nearly 4 times per hour.
I own 2 of the higher-rated Cascade series and all I can say is that these canister filters are pretty much a gold mine.
In fact, from what I’ve seen, they’re the most common canister filter of choice, and I consider that to be for a reason.
The price is more than reasonable, as far as these quality filters go.
Anyway, if you’d like to benefit from the additional bells and whistles that Fluval offers over the Penn Plax, you can for the Fluval 207 Series.
The Fluval 207 will provide your 30-gallon fish tank with pretty much the same GPH rate, but has its own advantages. You can check my thoughts about this unit in my review post about canister filters, which I linked to earlier in this article.
Moving on, my experience has been that the Fluval 407 would be able to handle a 40-gallon tank that’s decently stocked with fish.
The 407 Performance Canister Filter has a solid flow rate of 245 GPH, which is likely enough to handle a very overstocked 40-gallon Breeder tank.
Aquariums of this size are often heavily planted and house plenty of community freshwater fish.
Trust me you’ll end up like that one day.
With the 407 Canister Filter and the proper filtration media, you can keep whatever you want in there.
6. Optimum Canister Filters for 20-Gallon Fish Tanks
When it comes to canister filters for 20-gallon freshwater aquariums, the best ones would be:
For filtering 20 gallons of aquarium water I’d go with either an Eheim 2215 Canister Filter or a Fluval 107. With these units, I’d get a water turnover of about 5 times per hour for my fish tank. This is more than enough to keep my smaller aquariums debris-free.
Eheim is a big brand in the fish-keeping gear industry for a reason. From what I’ve seen (and owned) it is not uncommon that a filter of theirs would run for 7+ years.
Another quality of Eheim’s canister filters that I like is how much media they can hold.
They have plenty of room to house beneficial bacteria which is essential for a stable biofilter.
This makes Eheim ideal for smaller fish tanks – they don’t have a lot of flow to disturb the small swimmers while keeping ammonia and nitrite spikes at bay, thanks to their large filter media trays.
In smaller tanks of 10 to 20 gallons this is very important, especially when you’re adding new fish.
Add too many new fish at once and the organic waste produced will surely overwhelm the ammonia-converting bacteria.
From there the fish tank can get ammonia poisoning which is known to be quite deadly to aquarium fish. If not that you will get a nitrite spike, which can also be lethal, especially to freshwater species of fish.
Because of this and my bitter experience as a young fishkeeper, I recommend a filter that’s actually rated for up to 40 US gallons.
It’s not an overkill – it’s, in fact, completely justified.
Both the Fluval 107 and the Eheim 2215 can maintain a similar flow rate of about 95 GPH. The guys from Fluval are rather transparent about the data, but Eheim doesn’t really disclose the number.
What I did to calculate Eheim’s GPH rates was to compare their pump output (which they publicly disclose) to other filters with similar pumps, structure, and volume of the media trays.
Anyway, for 20-gallon aquariums that are heavy on livestock, the water turnover will be significantly slowed down. Add the filtration media to that and the flow can be reduced by a third or more.
If you’d like to overstock your 20-gallon fish tank, I’d recommend going for Fluval’s 207 Series Canister Filter.
The 207 has an hourly turnover rate of about 120 gallons, which will keep your heavily stocked 20-gallon tank in check by circulating its aquarium water volume 6 times each hour.
What I enjoy the most about Fluval’s canister filters is that, aside from their consistent flow rate, they also come with a plethora of added bells and whistles and are really easy to maintain and operate.
Note that for a 20-gallon aquarium that’s long, I would recommend getting a spray bar for the return outlet of your canister filter of choice.
As these water tanks are notably shorter in height your fish will have less space to swim up and down.
Also, if you’re planning to keep long-finned fish such as black skirt tetras, betta fish, pygmy goldfish, etc. you should definitely get a spray bar.
In my experience, a spray bar will reduce the pressure under which the water is being returned to the aquarium.
That way the incoming water flow won’t disturb the swimming of long-finned aquarium fish.
If you only keep community fish who like to dash back and forth such as Danios, a spray bar would not be needed as they will enjoy the stream.
7. Optimum Canister Filters for 10-Gallon Fish Tanks
The best canister filter for a 10-gallon fish tank is, in my personal experience, the Eheim 2211 Classic Filter. It will turn 10 gallons of aquarium water about 5 times per hour. This flow rate will keep the small fish tank free of debris and other free-floating particles.
I have estimated that the Eheim 2211 has a flow rate of about 45 GPH, which is not to be confused with its pump output GPH.
I did this calculation myself because Eheim only disclosed the pump output rates of their canister filters.
Anyway, with lightly stocked 10-gallon aquariums, a canister filter is not necessary. Your aquarium fish will likely do just fine with a sponge or HOB filter (link to see an excellent one on Chewy).
The pros of a canister filter for such a small fish tank are that it will provide awesome filtration while being visually hidden and especially quiet.
I would say that a good reason to go for a canister filter here would be if the aquarium sits in your or your children’s bedroom.
It’s important to remember that a small aquarium will get dirtier way faster, because of the confined space. As dangerous ammonia can build up pretty quickly in such a small volume of water, proper filtration is of utmost importance.
In my observations, most smaller fish tanks end up overstocked.
For this reason, you should, as with all aquarium filters, aim for a canister one that’s rated for a larger aquarium, hence my recommendation for the Eheim 2211.
That being said, for a heavily overstocked 10-gallon fish tank that houses a lot of “dirtier” fish such as plecos or pygmy goldfish, the proper canister filter would be:
The Eheim 2213.
It’s what I can certainly recommend in this situation.
This filter is rated for up to 66 US gallons (visit the link above to check the unit on Chewy). This rating is based on an empty unit with no filter pads, running on an aquarium with nothing but water in it.
Filter media, how often you clean the canister, and the aquarium decor all impede the flow rate of a filter.
Still, the Eheim canister filters are, in my observations, absolutely perfect for fish tanks with a volume of 10 to 15 gallons.
The units run quietly, do not blow your smaller aquarium fish and plants around, and provide outstanding filtration.
Anyway, here are some pieces of advice on these filters, that I must mention:
Don’t use the fine water-polishing pad that comes with the EHEIM filter. It will surely make your water crystal clear for less than a day, but you’d have to clean it 2 times a week and, trust me, that’s a LOT of work.
I would just double the coarse filter media instead.
Another thing that I should mention here is the instructions for setting an Eheim filter up and priming it. As radical as it might sound, the instructions are complete garbage. Worry not though.
Enter: the Internet.
There are hundreds of people who have that filter already and know how to best operate it and set it up.
You can easily find a video of one such person who shows you how to start and prime the unit.
Finally, I want to mention something about the INCOMING water flow. In a smaller fish tank, the fish can be more sensitive to the current. To avoid issues you have 2 really simple solutions:
- Drill small holes in the output pipe to spread the stream of returning water. Making 3-4 holes will be more than enough.
- Adjust the return pipe to point towards the back glass of your tank. This will soften the return flow.
Anyway, these are the best possible canister filters for all aquarium tank volumes.
Let me know in the comment section what I ended up with, or simply ask a question.