Answering the question, What is the best type of filter for freshwater aquariums is incredibly hard to do with zero context. Just like many things in this hobby, it really just depends. Different filtration systems are recommended for different uses. Theoretically, you can use any filter for any situation, but doing so may not be the best option. This article will go into detail on some of the reasons one filter system may be used over another. I will discuss sponge filters, hang-on back filters, internal canister filters, canister filters, and sumps.
Sponge Filters
An aquarium filter sponge, or just a sponge filter, is a very simple filtration system often used in freshwater aquariums. The mechanics behind this filter are pretty straightforward. The sponge is often built around a plastic housing, an airline tube connects to the housing, and the other end of the tube is connected to an air pump.
The air pump blows air through the tube, which creates water movement through the sponge. This forces water to move through the sponge, and this is how the sponge filter collects debris. I have another article discussing sponge filters; consider taking a peek at Sponge Filter Use, Cleaning and Extra Tips. Sponge filters are the most basic of filtration systems, but they can be incredibly useful in certain situations.
Best Uses for Aquarium Filter Sponge
Sponge filters can be incredibly versatile tools in freshwater aquariums, even with their simplicity. Their “best uses” come from the combination of gentle filtration, biological support, and ease of maintenance. I usually recommend them for aquariums that have low bioloads and smaller aquariums. They can be used in larger fish tanks, but I prefer using other filtration types for those. The following are key moments I would recommend using a sponge filter.
1. Gentle Filtration for Fry and Small Fish
Sponge filters provide strong biological filtration without creating strong currents that could stress or injure delicate fry, baby shrimp, or sensitive species like guppies, bettas, and hatchetfish. The sponge acts as a soft barrier, preventing tiny fish from being sucked into the filter while still allowing water flow. Unlike many other filtration systems, there is essentially zero chance of fish or shrimp getting sucked into a sponge.
2. Biological Filtration
The porous surface of the sponge provides a large area for beneficial bacteria to colonize. These bacteria break down ammonia and nitrites into less harmful nitrates, making sponge filters excellent for supporting the nitrogen cycle. Some hobbyists go so far as to “store” extra filter sponges in other aquarium filters to use for hospital tanks in emergencies. They can also be used to seed new aquariums, which accelerates the nitrogen cycle.
3. Supplemental Filtration in Breeding or Hospital Tanks
Sponge filters are ideal in quarantine, hospital, or breeding tanks. They clean the water gently while minimizing the risk of harming fragile or stressed fish. Because they’re air-driven (or can be powered by a gentle pump), they don’t disturb the tank’s setup or create strong currents that could dislodge eggs or fry.
4. Low-Cost and Energy-Efficient Filtration
Compared to canister or hang-on-back filters, sponge filters are inexpensive, simple to install, and use minimal energy (often just an air pump). When using a good-quality air pump, they can be incredibly quiet. If you have a silent air pump, the only thing you’ll hear is a quiet hum from the motor and bubbles breaking the surface of the water. For maintenance, simply rinse the sponge in fish tank water during a water change every few weeks to keep it effective.
Most aquarists consider changing out their sponge only when it starts to disintegrate. I recommend placing a new sponge into the aquarium weeks before removing the old one. This allows bacteria to colonize the new sponge, which will help prevent your aquarium’s nitrogen cycle from crashing.
There are many different air pumps you can use for your sponge filter. I have used the HITOP Aquarium Air Pump for a handful of fish tanks. I enjoy using this one because it has two air hose outlets that can be used on two fish tanks. Bonus points, it’s in the shape of a shark. Don’t forget to install the check valve to make sure water does not siphon back through the tube.
Another air pump that I recommend is the Hygger Aquarium Air Pump. It has fantastic reviews. One common thing aquarists really rave about is how quiet it is, which may or may not be rare with air pumps. The last thing you’ll need is the sponge, which the AQUANEAT 3 Pack Aquarium Sponge Filter should work without issue.
5. Great for Planted Tanks
Since sponge filters don’t generate strong currents, they’re perfect for planted tanks where you don’t want delicate plants uprooted or CO2-rich water disrupted. They provide excellent water movement near the surface without disturbing the substrate.
Sponge filters shine in situations that require gentle water flow, strong biological support, and minimal risk to small or delicate fish. They’re best used in fry tanks, shrimp tanks, small community tanks, planted tanks, and quarantine setups. They’re versatile enough to supplement larger filtration systems in bigger aquariums as well.
Downsides to Consider
Every filter will have some drawbacks. The sponge filter, although great, is a small and inexpensive piece of equipment, so it has its flaws. The following are negatives to sponge filters.
- Limited Mechanical Filtration
- No Chemical Filtration
- Takes up real estate in the aquarium
Regardless, the sponge filter has its place in this hobby. The popularity of this filtration system has grown. It is a biological powerhouse and can hold its own in low bioload aquariums.
Hang on Back Filters
Next on the list are Hang-on-back (HOB) filters. They are some of the most popular and practical filtration systems in the aquarium hobby because they balance power, convenience, and versatility. Their design makes them easy to install and maintain while providing strong, multi-stage filtration. My favorite part of hang-on back filters is that they allow you to customize filter media and also to provide chemical, biological, and mechanical filtration in your aquarium.
At the moment, the Seachem Tidal is one of my favorite hang-on-back power filters. It comes packed with an incredible number of features for such a compact design. Seachem Tidal Power Filters are made in different sizes for different needs. I recommend using power filters for aquariums with low to moderate bioloads. If you are housing large waste-producing fish or large bioload aquariums, consider looking into canister filters and sump systems. There are plenty of HOB filter brands; check out 7 Best Hang On the Back Power Filters for Freshwater Aquariums to see a handful of them. The following are a few reasons you might want to use a hang-on back filter for a fish tank.
1. General Community Aquariums
HOB filters are ideal for standard freshwater setups with small to medium-sized fish, like guppies, tetras, mollies, and gouramis. They provide efficient mechanical, biological, and chemical filtration, keeping water clear and healthy with minimal maintenance. The beauty of many HOB filters is their customizability. You can change filter media to fit your style, depending on the needs of your fish.
2. Tanks Requiring Moderate to Strong Flow
Because they create a steady current and surface agitation, HOB filters are excellent for tanks that benefit from good oxygen exchange and water movement. It’s perfect for active swimmers like danios, barbs, and rainbowfish. The flow also helps prevent stagnant areas where debris can build up. Often, additional water movement and oxygen exchange are not needed if a hang on back filter is running in your aquarium.
3. Aquariums Where Space Inside the Tank Is Limited
Since hang-on back filters sit outside the aquarium, they save valuable interior space for fish, plants, or decorations. This is especially useful for smaller aquariums or aquascaped tanks where aesthetics matter. Unlike a sponge filter that can take prime real estate in an aquarium, the only thing you’ll see in your aquarium with a HOB filter is the intake tube.
4. Tanks Needing Easy Maintenance
One of the biggest benefits of HOB filters is accessibility. You can change cartridges, rinse sponges, or adjust media without disturbing your aquascape. This makes them fantastic for beginner aquarists or anyone who prefers quick, low-hassle maintenance.
5. Supplemental Filtration for Larger Tanks
In larger setups, a HOB filter can serve as a secondary or backup filter to boost circulation and biological filtration alongside a canister or sponge filter. Many aquarists use them to polish the water or run chemical media (like activated carbon or Purigen) to remove discoloration and odors.
6. Great for Quarantine or Backup Systems
Because they’re easy to move and install, HOB filters are a good option for temporary or quarantine tanks. Personally, I prefer using sponge filters for quarantine tanks, but to each their own. You can even keep spare sponges and other media in the hang-on back filter media basket for easy removal. The media, such as a sponge, will be seeded with bacteria, making it great to pull for a quarantine or hospital tank.
Downsides to Consider
HOB filters are fantastic, and perhaps the most popular filtration system available. They’re not perfect, and there are some downsides to running power filters.
- Waterfall creates noise
- Takes up external space
- Re-Priming issues
Not all hang on back filters are created the same. Some have motors that sit inside the fish tank. This makes the final point of re-priming issues negligible. However, some filters have external motors. When the power goes out, there is a likely chance that the filter will not re-prime itself (start a siphon). The motor will turn on, but it must be primed again to get water moving. This can cause issues with your motor running dry, overheating, and burning out.
Internal Canister Filter
People either love or hate internal canister filters. They have their space in the hobby, and the love for these filters seems to be growing. However, many people lean towards using sponge filters, HOB filters, or external canister filters over these. Once I gave an internal canister filter a shot, I began to really enjoy using them. The following are a handful of reasons why you might want to use an internal canister filter. There are some downsides to using this filter.
1. Medium-Sized and Medium Stocked Tanks
Internal canister filters work well for medium aquariums (20–55 gallons) or tanks with a low to moderate bioload. I would personally not use this as the main filter for Mbuna & Peacock aquariums, but I would consider using an internal canister for an aquarium that houses one or a few medium-sized cichlids. An internal canister should have no issue handling the bioload of a pair of angelfish. I would use an internal canister filter as a supplemental form of filtration and for additional water movement, for heavily stocked fish tanks.
2. Aquariums Without Room for External Filters
If your tank setup doesn’t allow space behind or under the aquarium (such as wall-mounted tanks, custom stands, or aquariums against a solid wall), internal canisters are perfect. They sit neatly inside the tank, keeping the setup compact and self-contained.
3. Turtle or Semi-Aquatic Setups
Because they operate fully underwater, internal canister filters are ideal for turtle tanks, paludariums, or shallow aquariums where a HOB filter might lose suction. They handle waste better than simpler sponge systems. Internal Canisters can be large in size, so very shallow paludariums may not be able to use them.
4. Strong Biological and Mechanical Filtration in Smaller Tanks
Internal canisters often feature multiple chambers for different filter media. You can often use sponges, ceramic rings, activated carbon, and other filter media. This provides true multi-stage filtration without requiring an external unit. This makes them excellent for planted or display tanks that need crystal-clear water.
5. Quieter Filtration Solutions
Since the entire unit operates underwater, internal canister filters are remarkably quiet, making them ideal for bedrooms, offices, or other spaces where noise is a concern. For some of us, this is a game-changer. I love my aquariums, but I also enjoy sleeping in silence. The sound of flowing water drives me crazy when I am trying to sleep. This is partly why I do not keep aquariums in my bedroom. I may test an internal canister filter in my bedroom one day to see how silent it truly is.
If you’re in the market for internal canister filters, consider giving the Sicce Shark PRO Internal Aquarium Filter or OASE Bioplus a shot. At the time of this writing, I have a Sicce Shark PRO Nano waiting to be used, and I am incredibly excited to give it a test run.
Downsides to Consider
Internal canisters are fun devices, and as stated earlier, have their place in the hobby. They’re quite versatile, but do have their drawbacks. The following are a few that I can name.
- Visually Intrusive by taking up space inside the fish tank
- Compact, which makes small spaces for media
- Mess can be made when pulling the filter out for maintenance
Some might not be bothered by the small media space, but it’s definitely something to think about when considering fish stocking.
Canister Filter
Next, we are moving on to the external canister filter. These filters are powerhouses, often used for heavily stocked aquariums, aquariums with large fish, or enormous fish tanks. They come in a variety of sizes and fill a variety of needs. Canister filters make room for mechanical, biological, and chemical filtration and are fully customizable to your specifications.
Fluval Canister filters are often considered some of the best canisters, but there are many options to choose from based on budget. The Fluval 207 covers the needs of aquariums up to 45 gallons, and the titan, that is the Fluval FX6 Canister Filter is rated for fish tanks up to 400 gallons. The following are situations where I would recommend using a canister filter.
1. Large or Heavily Stocked Aquariums
Canister filters shine in tanks 40 gallons and up, especially with large or messy fish like cichlids, goldfish, or plecos. They can handle high bioloads with ease and maintain stable, clean conditions even in demanding environments. Larger fish produce larger waste. Sometimes this waste cannot be removed with hang on back filters or other filtration systems. That is where the canister filter shines.
2. Display and Planted Aquariums
Because the entire unit sits outside the tank, canister filters keep the interior looking clean and uncluttered. Besides the intake and outtake tubes, there is no bulky equipment visible inside an aquarium. They’re perfect for show aquariums or planted tanks where aesthetics matter, and you can customize the media for gentle flow and water clarity.
3. Tanks Requiring Customizable Filtration
Canister filters often have multiple media baskets, letting you tailor filtration to your specific needs. Whether that’s to boost biological filtration with ceramic rings, polishing water with fine floss, or removing tannins with activated carbon. This customization makes them an incredibly adaptable option.
4. Aquariums Needing Strong Circulation
These filters provide excellent flow and turnover, helping distribute heat and oxygen evenly throughout the tank. This can be crucial for large aquariums or those with dense aquascapes. Dead spots in water can cause detritus and debris to build up, which is not great to have happen.
5. Quiet and Efficient Long-Term Operation
Once primed and running, canister filters are extremely quiet. Their sealed design also reduces evaporation and splashing, which helps maintain stable water parameters over time.
Downsides to Consider
The size and versatility of canister filters make them incredible for large fish tanks. However, with this comes some drawbacks. I’ve used plenty of canister filters in the past, and the following are flaws to using them.
- Cleaning can be time-consuming, as the unit must be disconnected and opened for maintenance
- Can be bulky, requiring cabinet space below or beside the aquarium
- If not maintained, flow can decrease over time as debris clogs the media
- Improper setup (like kinked hoses or air leaks) can cause performance issues
- More expensive upfront
Canister filters are ideal for large or heavily stocked tanks, high-end planted aquariums, and situations where water clarity and stability are critical. While they require more effort to maintain, their performance, quiet operation, and flexibility make them one of the best filtration systems available for serious hobbyists.
Sump System
A sump is essentially a secondary tank, usually located below the main aquarium, that houses filtration equipment, media, and sometimes additional gear like heaters, skimmers, or probes. Water from the display tank flows down into the sump (via an overflow system), gets filtered through multiple stages, and is then pumped back up into the main tank. This setup not only provides exceptional filtration capacity but also improves water stability and gives aquariums a clean, equipment-free look.
If you’re in the market for a sump system, but don’t want to break the bank on a pre-built unit. Consider purchasing an adjustable sump baffle kit. These kits are made to fit different aquarium sizes, and are often quite cheaper than purchasing a pre-built sump. Leave room for a return pump and access to plumbing when sizing out each stage of the sump system.
1. Large or High-Bioload Aquariums
Sumps are ideal for large tanks (75+ gallons) or those with heavy bioloads, such as cichlid tanks, discus setups, or marine systems. They dramatically increase total water volume, which helps dilute waste and stabilize parameters. This is something smaller filters can’t match.
2. Advanced Freshwater and Saltwater Displays
Because all the filtration and heating equipment can be stored out of sight in the sump, the main tank looks clean and natural. This makes sump systems the top choice for planted aquascapes, reef tanks, and show tanks, where aesthetics matter as much as performance.
3. Custom and Modular Filtration Needs
Sumps are highly customizable. You can include filter socks, sponge stages, bio-media chambers, reactors, or even refugiums for live plants and beneficial bacteria. This modular design lets you fine-tune your filtration for any setup.
4. Improved Water Stability and Oxygenation
Because sump systems increase total water volume and surface agitation, they make temperature and chemistry changes more gradual and help maintain excellent oxygen exchange. This is particularly valuable for sensitive species like discus.
5. Quiet, Hidden Operation
When properly designed, sump systems are very quiet and eliminate the need for bulky equipment in the display tank. Heaters, probes, and even CO₂ diffusers can all live in the sump, keeping the main tank uncluttered.
Downsides to Consider
- More complex to set up than standard filters. Requires plumbing, an overflow system, and a return pump
- Higher upfront cost, especially if built custom or professionally installed.
- More space is required, as a sump usually sits under the tank in a stand or cabinet
- If not properly designed, flooding can occur during power outages or overflows
- Maintenance can involve cleaning filter socks, managing pumps, and occasionally refilling evaporated water
Sump systems excel in large or heavily stocked tanks and allow near-endless customization of filtration and equipment. While they require more setup, space, and maintenance than simpler filters, their performance and expandability make them the gold standard for advanced freshwater systems.
Final Notes
The best filter is the one that is properly sized and maintained for your specific aquarium ecosystem. There is no single “perfect” device; rather, a spectrum of tools designed to meet different needs. The Sponge Filter is ideal for breeding and fry tanks where gentle flow is a necessity. The Hang-on-Back (HOB) Filter offers the best balance of simplicity, customizable media, and easy maintenance for small to mid-sized tanks. For large, heavily stocked, or complex aquascapes where maximizing filtration volume and minimizing visual clutter are key, the powerful Canister Filter is the superior choice.
Always remember that a filter’s efficiency is only as good as its biological media, and no filter can replace the necessity of consistent, partial water changes. Choose a filter system that is easy for you to maintain, and you will set your tank up for long-term health and success.