Saltwater aquarium filters are critical to providing a healthy environment for your fish and invertebrates. As Jessica Fox, DVM, CertAqV puts it, “filtration is a key component to ensuring your fish and invertebrates stay healthy in their aquatic environment.”
Your filter is responsible for removing particulates from your water and providing a home for beneficial bacteria powering your biological filtration. It will take your filter 4-6 weeks to build up these colonies and avoid “New Tank Syndrome,” so be sure to check your water quality regularly and be ready with some extra salt water for any necessary water changes.
Your best filtration option will depend on your tank size, water volume, and bioload (total tank inhabitants). Our favorite saltwater aquarium filter for the widest range of configurations is the Aquaclear Power Filter, which is durable and easy to use.
If you are adding a new filter to an existing setup or getting a new tank started, here is a check list to ensure you haven’t forgotten anything!
Fluval AquaClear 50 Power Filter
Excellent filter media
Good for various sizes of tank
Easy to clean
Not self priming
The AquaClear Power Filter. This filter comes in a variety of sizes for many different aquarium setups. Each filter includes a durable sponge filter, carbon and zeolite media. The media can be changed out per user preference and additional options can be added if desired.
The AquaClear Power Filter is very easy to set up and clean. There is a small plastic foot that is required to keep the filter level, so make sure you don’t lose it! The basket inside the filter makes the media easy to remove and clean. The flow is adjustable, making it perfectly suited to many slower swimming fish and delicate corals and other invertebrates.
In addition to being easy to clean and very customizable, the AquaClear filter has a very reasonable price point. The filter media will last you for years, making this filter a very sound investment for any aquarium. Not only for saltwater, the AquaClear filter can also be used for freshwater and brackish aquariums.
Price at time of publish: $60 for 20-50 gallon filter
Dimensions: 4 x 9 x 8 | Gallons Per Hour: 200 | Tank Size: 20-50 gallons
Fluval Performance Canister Filter
Multiple filtration media (included)
Easy to use
Can be difficult to clean
Have to set intake and return correctly
The Fluval Performance Canister Filter should be your first consideration if you'd like to hide your filter from view. Canister filters move the filtration under your tank and allow for multiple configurations. The Fluval Canister Filter is quiet, with good reliability, in addition to full customization options.
It has a well-designed housing too, with ergonomic valve connections and locking clamps that make running filter pipe relatively painless. There is no evidence that illustrates whether hang-on versus canister filters have better performance, and both require some proper setup and knowledge.
When setting up your canister filter, take into consideration where the intake and return should go in your tank. The right placement should prevent zones of strong current from forming, unless you have lots of strong, active swimming fishes in your tank.
The Fluval Performance Canister Filter is available in four sizes, for tanks up to 100 gallons.
Price at time of publish: $145
Dimensions: 7 x 7.5 x 16.5 inches | Gallons Per Hour: 206 | Tank Size: 45 gallons
Tetra Whisper Power Filter
Low price point
Multiple filter gradients
Filter media not durable
The Tetra Whisper Power Filter comes with less than ideal filter media, but you can easily swap it out for something more durable, significantly improving the performance in this impressive budget pick. The Tetra Whisper Filter comes with a dual motor setup in its larger filters, for reliable, backup performance.
It's quiet, effective, with a proven design, but we have encountered an issue that causes its magnetized motor to stop running. If your motor stops running, the best thing you can do is move the intake just off to the side and take a skewer or chopstick and gently turn the rotor. Our office has revived many a “dead” pump using this method.
Price at time of publish: $57
Dimensions: 5.8 x 8 x 13.6 inches | Gallons per Hour: 330 | Tank Size: 40-60 gallons
Best Internal Power
Fluval U Series Underwater Filter
High quality sponges
Easy to clean
More involved setup
Highest price for internal filter
Per one of our previous write ups, the Fluval Underwater Filter is the top of the internal aquarium filter line. This internal filter is better for smaller setups, but has many options for customizing your filtration media and outflow options. There are four filters in the product line that may be suitable to your smaller saltwater aquarium.
Internal filters differ from other filters in this list in that they sit inside your tank. In doing so, they may decrease the total volume of your tank and take up room from your other tank inhabitants. These filters are typically not that strong, so do not ask them to do too much heavy lifting in a larger or heavily overstocked tank.
Price at time of publish: $51
Dimensions: 6 x 3 x 4 inches | Gallons per Hour: 105 | Tank Size: 30 gallons
Fiji Cube Refugium Sump Baffle Kit
Pre-segmented into chambers
Adjustable water level
Includes space for protein skimmer
Media and refugium
Have to provide your own filter media
Tank not included
A sump is essentially a large, open filter for your saltwater tank. They do take a little bit of finesse and practice to optimize water flow and ensure your sump level stays consistent with the above water level. This kit includes the following components: a filter sock holder, which holds three filter socks; three filter sock silencers; three filter socks; two bio-foams; and two media trays, in addition to multiple adjustable slots that allow for an immense range of component choice and customization.
Sumps are common in saltwater systems, but they are not a requirement. Some aquarists use refugium, which acts essentially like a living filter, and usually contains some type of macroalgae, and may even have a few invertebrate or fish cohorts. These require a secondary light in order for your algae to grow and thrive.
Price at time of publish: $115
Dimensions: N/A | Gallons per Hour: N/A | Tank Size: 20 gallons
Aquatop FORZA Power Filter with Surface Skimmer
Dual motor and return
Adjustable flow rate
Poor filter media (easily replaced!)
Intake can get clogged
Requires specific water level for optimum noise and efficiency
If your tank is prone to a scummy surface, you may want to consider incorporating a surface skimmer, such as the one built into the larger models of the Aquatop FORZA filter. The rest of this filter is built very similarly to the other hang-on filters mentioned here, but the intake has a skimmer feature incorporated that will suck surface debris right into your filter. The attachment does not have great water level adjustability, so ensure your tank water level remains at the optimum height for correct function.
For heavy scum levels, you should consider incorporating a protein skimmer. These filtration components are made to handle heavier bioloads then this little skimmer can handle. For smaller setups or saltwater tanks without many inhabitants, the Aquatop FORZA skimmer can get the job done effectively.
Price at time of publish: $49
Dimensions: 14 x 11 x 6.5 inches | Gallons per Hour: 300 | Tank Size: 100 gallons
Best Nano Internal
Fluval Nano Aquarium Filter
Low flow for sensitive fish and invertebrates
Durable filtration media
Limited filtration capability
Not suitable for any tanks larger than 15 gallons or small tanks with lots of fish and invertebrates
Nano tanks, another description for aquariums under 40 gallons, require smaller equipment and are only suitable for a small collection of fish and invertebrates. It can be very easy to overstock these small systems, which can put considerable strain on your filtration. The Fluval Nano Aquarium filter incorporates a robust filter sponge with a return through a spray bar, decreasing the amount of current in your small system. This is ideal for these nano tank inhabitants.
As with other internal filters, the Fluval Nano Aquarium filter will take up some of the real estate within your tank. It also allows access to the bacterial detritus to your tank inhabitants, which in the case of shrimp, will cause them to try and enter your filter. Provided they are large enough to remain outside of the intake slits, this should not be a problem. But if you have reproductively active populations, small individuals may get stuck inside your filter and require gentle extraction.
Price at time of publish: $21
Dimensions: 2 x 2.75 x 7.5 inches | Gallons per Hour: 30 | Tank Size: Up to 15 gallons
Best Nano Canister
ZooMed Nano External Canister Filter
Adjustable water flow
Improved filtration capacity for smaller tanks
Multiple filter media options
Limited filtration for any tanks larger than 30 gallons or overstocked systems
Intake and return need to be set correctly
External canister filters are not just for large tanks. An external canister filter, such as the ZooMed Nano Filter, can improve your tank’s overall filtration capacity without sacrificing internal space. This may be a better option for many smaller setups that have a lot of activity or individuals within the space. Remember: most nano systems work best with a low bioload since there is not much extra water to dilute out waste products!
As with all canister filters, setting up the intake and return are critical, especially within a small space. Try to position the intake and return at opposite ends of the tank and the return should be directed along the diagonal axis of the tank in order to decrease the formation of any strong currents. If you have delicate fish or invertebrates in your tank, you may want to consider the internal nano filter above instead of the canister option.
Price at time of publish: $79
Dimensions: 12.5 x 7.4 x 7.6 inches | Gallons per Hour: 80 | Tank Size: Up to 30 gallons
Best for Large Tanks
Fluval High Performance Aquarium Canister Filter
High filtration capacity
Customizable filter media
Twin output return
Overpowered for small aquariums
Have to setup intake and return correctly for best function and filtration
Big tanks require lots of filtration, especially if they contain a lot of fish and invertebrates. The Fluval FX series provides lots of filtration capacity with a highly variable setup. You can customize the included filter media to suit your tank’s needs. This canister also comes with a self-priming feature and a 90° dual return to decrease any strong current formation from this formidable filter.
For some tanks, bigger, bolder filtration isn’t always the best option, especially if you have delicate fish, soft corals or special-needs inhabitants who require lower water flow. The Fluval FX filter series is made to handle large bioloads and at 925 gal/hour filtration, you will turn over a significant volume of water. If your tank does not have a high fish load or has fish that need slower water, you may want to combine two smaller filters to get the job done.
Price at time of publish: $370
Dimensions: 15 x 15.5 x 21 inches | Gallons per Hour: 925 | Tank Size: 250-400 gallons
Our Best Overall pick in Saltwater Aquarium Filters is the Aquaclear Power Filter. It is a durable, easy to use product with a filter media that will last for years! If canister filters are your preference, you can’t go wrong with the Fluval Performance Canister Filter in a wide range of sizes, all of which provide exceptional customization of your filter media.
What to Look for in Saltwater Aquarium Filters
As with any aquarium component, read the instructions carefully before you setup your new filter. Although many may look similar, tiny differences in set up and filter placement can have a huge impact on how efficiently your filter works. Pay special attention to any filters that have a set water line and mark it clearly on your tank.
Hang-on Filters: These filters “hang-on” to the side of your aquarium and have a long intake that will stick into the middle of your water column. Return to your tank is a waterfall that provides aeration in addition to aesthetic value. Sometimes, these filters will have a little foot at the base in order to ensure they are level from front to back.
- Canister: Canister filters are externally located, usually resting under your aquarium. They will have an intake and return tube that can be placed anywhere in your aquarium. For proper function, they should be placed at opposite ends of the tank with the intake placed near the bottom of the tank and the return close to the surface. This will create a gyre-like current in your tank, circulating all of the water. If the intake and return are placed too closely to each other, you will only be filtering a portion of your water. If the return is incorrectly directed, you may create fast currents that can be hard for fish and invertebrates.
- Internal: Internal aquarium filters remain on the inside of your aquarium. Like hang-on filters, these require a clip or suction cup to keep them in place, but they take up space within the aquarium. These are best for smaller systems who do not require much space and lower flow.
- Sump: A sump filter is a separate tank that sits under your aquarium and can contain multiple filter components. Sumps allow for more control over various filtration elements but can be difficult to set up correctly. Water level and balance between the sump and main tank can be tricky and it is critical to have backup methods in place in case of power failure so your tank does not back siphon and accidentally drain.
Tank size will vary depending on the fish and invertebrates you want in your tank. There is no hard and fast criteria for how much room each fish will need and “one gallon of water per one fish” is not a valid rule. You should carefully consider all of the species you want to accommodate and then provide additional water and space. Additional water will allow you to some cushioning if your filters are not well established or you miss a water change or two. Additional space will allow for fish and inverts who do not behave as expected to be allowed space to feel comfortable. Just because one species of fish is supposed to be a “communal” species does not mean all individuals will follow the rules!
Many filters will come with media components, but many will not last long. No matter what it says on your filter, do NOT throw away your filters every few weeks or months. You have worked very hard to cultivate these critical bacterial colonies for your nitrogen cycle; why would you just throw them away? Carbon is typically not essential for most aquarium systems and a few granules in your filter will not make a significant difference. Zoelite or ammonia-scrubbing components have a set shelf life and can still be beneficial once their absorbing power is complete. Sturdy sponges, such in the AquaClear filter, are the best overall and many can be cut to fit any size filter.
Gallons Per Hour
Most aquarium filters are listed with an approximate size tank gallons. Most will have a size that is approximately ½ to 1/3 of the total gallons per hour of the tank. This means that the tank water will be cycled 2-3 times per hour. This is the best gage for measuring if your filter will be sufficient for your tank, but is not set in stone. Many aquariums are overstocked, requiring additional filtration, but a larger filter can create a faster current which can be very problematic for your fish and inverts. Sometimes, multiple lower-powered filters will be best for your setup. It can be challenging to experiment with various setups until you find the best one for you and your tank inhabitants.
Are canister filters bad for saltwater aquariums?
Canister filters are not bad for saltwater aquariums. As with any aquarium, either saltwater or freshwater, filtration is critical to providing a healthy environment by removing particulates and allowing beneficial bacteria to grow and provide nitrogen cycling (link). No matter what type of filter you use, including canisters, complete filtration of all of your aquarium water is critical. It is better to ensure your filter is properly sized for your aquarium than worrying about the type of filter. Large systems may work best with multiple filters or require powerheads to provide acceptable circulation throughout the tank.
Are saltwater and freshwater filters the same?
Yes. Any filter can be used for both saltwater and freshwater aquariums. There is no filter that is better for saltwater or freshwater. You cannot switch a filter from a freshwater aquarium to saltwater tank and visa versa without decontaminating it first. However, if you properly clean a filter or provide fresh filter media, you can swap out the unit between systems.
Can I use an undergravel filter with a saltwater aquarium?
Since most saltwater aquariums use live sand (link) as a substrate, you cannot use an undergravel filter. Undergravel filters can be used with larger substrate, such as gravel, but they are not recommended. They are exceptionally hard to clean and once they are clogged, the entire aquarium needs to be disassembled.
Why Trust The Spruce Pets
As a private practice fish veterinarian for 10 years, Jessie Sanders, DVM, CertAqV has considerable experience with the various filters available and their pros and cons. She herself has had an AquaClear in all of her tanks, one of which has been running for 8 years (with the same filter media!). Filtration is a critical component of tank health, so she greatly understand its importance and maintenance in order to guide her clients to the best solution for their tank. Often, it simply comes down to owner preference, since all of these systems will get the job done, provided they are the correct size for your tank and bioload.