Sump or Canister Filter – Which is Better for You?

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A good filtration system is vital to any closed aquatic setup. All aquariums require some form of filtration, but given that there are several filtration options available, which should you choose?

Today, we will discuss 2 of the most popular filter units: sump and canister filters. What’s the main difference between them, and which should you go for? Let’s have a look.

What is a Sump Filter?

Sump filters are external systems that go underneath your main tank. The system itself is pretty much an ecosystem of its own, contained within another tank.

The setup is rather large since it needs to house several large components, making it more fitting for larger aquariums.

Most aquarists use sump filters for 150-200-gallon tanks or larger, depending on their goals.

The sump filter is quite an extensive system, providing mechanical and, most importantly, biological filtration to stabilize the main tank’s parameters. There are several benefits coming with a sump filter, but there’s no denying that this is a more complex system.

It’s more difficult to set up and get it working, but the maintenance process afterwards is relatively easy.

But how exactly does the sump filter works? The system itself comprises of several parts, such as a skimmer, a drain section, a mechanical filter, a bubble trap section, and a return section.

The latter is designed to carry the clean water back into the main tank.

The working process goes as such:

  • The weir and overflow – The weir is a subdivision of the main tank. It’s pretty much a different compartment that takes in excess water accumulating in the tank and spilling over in the weir. The weir houses the overflow attached to the drain pipe that goes down to the sump system. The overflow sucks in water from the main tank and takes it to the drain section.
  • Mechanical filtration – The mechanical filter traps all of the larger particles like sand, organic matter, plant residues, fish waste, food leftovers, etc. This cleans the water and keeps it clearer and healthier, preventing ammonia and nitrate buildup. The mechanical filter is the first process in line before the protein skimmer gets online.
  • Further cleansing and reoxygenation – This is where the protein skimmer comes in. The skimmer removes dissolved waste particles that the mechanical filter cannot stop. It will also reoxygenate the water by forcing gaseous exchanges via bubbling. The water will take on a foamy look, sort of like what you see on an ocean’s shores. Naturally, these bubbles may stress out your fish. So, it’s time for the final part – de-bubbling.
  • The bubble trap – Bubbles aren’t really a problem in freshwater tanks, but they’re not recommended in saltwater environments. Corals and saltwater fish don’t appreciate the foamy blanket of bubbles, so the bubble trap is necessary for this sense. The mechanism will trap all the bubbles, keeping the water clear while still well-oxygenated.
  • The return pump – This device takes on the purified water and returns it to the main tank. There, it will refill the aquarium, spill over in the weir, and restart the entire process.

Sumps are quite effective filtration mechanisms for larger, coral-based environments. Needless to say, they are rather difficult to operate, especially for a novice aquarist.

So, try to avoid sump filters as an absolute newbie at first.

Pros & Cons of Sump Filter

Naturally, the sump filter is by no means perfect. It has both pros and cons, depending on your setup, experience level, and expectations.

Let’s look into these:

Pros

  • Silent – No one can refuse a silent filtration system. Especially since the mechanism will function 24/7.
  • Improved biological filtration – No filtration system can keep up with sump filters in terms of biological filtration. After all, you have an entire ecosystem attached to your main tank. The fact that the sump filter is a separate tank itself allows you to perform more extensive biological filtration thanks to the extra room. This will result in a healthier, cleaner, and a more stable environment overall.
  • The weir – The weir keeps the water clean by preventing surface film. The surface film or surface scum is the natural result of plant and coral activity. The film itself is pretty much a mix of fat and dead matter accumulating on the substrate and reducing the system’s gaseous exchange. The result is poorly-oxygenated water and increased levels of nitrate and CO2. The weir prevents that by constantly taking in surface water that spills over into the separate container.
  • Highly customizable – Sump filters are highly customizable in terms of size, shape, chamber types, and the various filter media you’re looking to use. You can even pick where and how you position the sump filter in relation to your tank, based on your available space and vision. This is great when considering that most filters are pretty much the same, no matter their size.

Cons

  • Too complex – Sump filters are generally extensive mechanical and biological systems that aren’t quite user-friendly. Especially when the user is rather inexperienced in these types of filtration systems. I wouldn’t recommend sump filters to beginners for this reason.
  • Take up a lot of space – Sump filters don’t take up space in the main tank, but they need room nonetheless. Whether you place them under your tank or side-by-side, they will occupy a lot of space either way.
  • It needs a main pump – Some sump filtration systems come with a main pump, but not all. Without a pump in place, the filter is more prone to clogging and having gunk overwhelm the filter media faster.

Overall, I would say that sump filters are great for more experienced aquarists looking to entertain a larger, coral-filled tank.

What is a Canister Filter?

Canister filters rank as the most popular option in the aquarium business. Their operating principle is quite simple.

The filter uses a syphon to suck tank water, takes it to the filtration area, performs mechanical and biological filtration, and returns it to the main tank.

It’s a simple and clean process, but this isn’t the main reason why canister filters as so sought after in the industry. The main reason for that is their ease of use and the fact that they take up almost no space in the main tank.

Sump filters don’t take up any space either, but they’re far too complex compared to canister filters.

It also doesn’t hurt that canister filters are easy to clean without disturbing the main aquatic habitat and that they are quite effective at their job.

For instance, canister filters also hold much more media than other types of filters, like HOB (Hang-On-Back) filters.

This allows for improved biological filtration and less frequent maintenance work since the filter is less likely to clog.

Pros & Cons of Canister Filter

Here are some of the pros and cons of canister filters:

Pros

  • Easier to install and maintain – There’s no question about it, canister filters are far easier to use than sump ones. They are more fitting for beginners and intermediate aquarists as they’re not as technical in terms of installation and maintenance requirements.
  • Deliver more power – Canister filters are more powerful than sump filters. The external pump that comes with the package will deliver a high-water flow, forcing more water through the filter media. This allows the filtration system to achieve higher filtration results, improve the environment’s oxygenation levels, and clean the water faster. This is especially important in stacked tanks that show an increased risk of chemical or biological imbalances.
  • More durable overall – Canister filters come with additional water pumps and hoses that take some of the strain off the filtration system. This makes canister filters less prone to wear and clogging over time. As a result, you will perform less maintenance work, as your filter is sturdier and more effective in the long run.

Cons

  • Higher noise pollution – Unfortunately, canister filters are noisier than their slump counterparts. The noise isn’t necessarily a deal breaker, but you should consider this point, as it will influence your decision in terms of how and where you position the tank.
  • Ineffective against surface scum – Canister filters aren’t really effective at preventing surface scum or film. This is especially a problem in heavily planted aquariums, where surface scum is bound to form rather fast. So, you must perform regular maintenance and water changes to prevent that. Fortunately, you need to do that anyway to prevent algae overgrowth, reoxygenate the habitat, and dilute nitrates. After all, the filtration system can’t carry all the work for you.
  • Insufficient at times – You may need to invest in 2 canister filters at times in case your aquarium is extremely big. One filter may not cut it, as it only has limited power and isn’t really fit for extreme aquatic habitats. Sure, you can increase the pump’s power, but this will only create extreme water currents, hurting fish and plants. Many aquarists avoid this issue by investing in 2 filters, usually different, to ensure different filtration effects. For additional chemical purification, you can pair canister filters with a filtration unit based on activated carbon.
  • Clutters the tank – Canister filters will take up tank space, and there’s no way around it. The pump and the heater will displace some water in the process, but these are necessary to keep the environment healthy long-term.

Conclusion

Overall, I wouldn’t say that there’s a decisive winner between the 2 filtration systems. It all depends on your aquatic setup and overall goals and vision.

That being said, most people use canister filters for obvious reasons, the most relevant one being that they’re easier to use and maintain.

Naturally, sump filters come with their own benefits, so, ultimately, you have the final decision.

avatar I’m Fabian, aquarium fish breeder and founder of this website. I’ve been keeping fish, since I was a kid. On this blog, I share a lot of information about the aquarium hobby and various fish species that I like. Please leave a comment if you have any question.

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