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Choosing the right aquarium filter will have a profound impact on the stability and maintainability of your tank.

Most hobbyists will eventually decide on one of these two types of filters: the hang-on back (HOB) filter or the canister filter. Both have their place, but these types serve incredibly different setups and experience levels.

If you're unsure which of the two works for your tank, here's a quick guide to figure it out.

Quick Answer

If your tank is small and you want something simple, go with a HOB filter.
If your tank is larger or planted and you want stability in the long term, pick a canister filter.

A simple way of viewing it for many hobbyists is:

• Small tank / Beginner setup = HOB filter
• Medium to large / Planted tank = Canister filter

What Is a Hang-on-Back (HOB) Filter?

The filter, which hangs off the back lip of your aquarium, works by drawing water up the pipe and out the other end through the media, which then reenters the tank.

These HOBs work fine for casual setups because they do great work for minimal effort with setup. They are designed to provide, generally, these types of filtration:

• Mechanical filtration-Removing chunks
• Chemical filtration-Removing toxins using something like Carbon
• Some Biological filtration-Beneficial bacteria population living in the filter

For a smaller home aquarium, this setup will often be perfectly fine for clear water unless you're overstocking your aquarium.

Real-World Experience from Home Tanks

HOB filters work perfectly fine in a smaller tank of 10-20 gallons with fish like bettas, tetras, or guppies. Many don't feel like they need to upgrade until

• Your tank is overstocked
• Or you're cleaning the filter quite often

What Is a Canister Filter?

These external canister filters work by being housed usually inside your aquarium cabinet and pulling water out from the aquarium and pushing it through different types of filter media before pushing the clean water back into the tank through the spray bar or outlet pipe.

With canister filters, the difference isn't necessarily just power, but how large a population of beneficial bacteria you are able to sustain in the long term. Since the filter media is housed outside the tank, it usually has significantly more volume than the equivalent HOB. This helps create more stability in large tanks and tanks that are overstocked.

Real-World Experience from Larger Tanks

As you get up into 40-75 gallon tanks that also may have a growth system planted into them and more stock within them, you will usually find a canister is significantly more effective and keeps water clear for a much longer duration than other filters.

This is not to say that HOBs are a "bad filter," they just hit their performance capacity sooner with a larger bioload than a canister filter does.

HOB vs Canister Filter: Key Differences

Instead of making this into a technical comparison, it's easier to view it in terms of how it feels to use one of these filters on a day-to-day basis.

Maintenance: What It's Like in Real Life

HOB Filter Maintenance

We will all mostly just pull it off the back, rinse out the sponge under the tap, and then replace it on the back of the tank. That's easy, and something you can do on the fly without having to plan a "project". That is why they are suitable for many beginners and allow us not to have to plan out a system that we have to work around.

Canister Filter Maintenance

Maintenance required is less often, but takes longer. In reality, you will have to:

• Turn the valves off to stop the water flow
• Remove the hoses
• Un-canister the filter
• Rinse the filter media trays

Cleaning them out takes longer, but you won't have to worry about cleaning them nearly as often.

Performance: What Actually Changes?

The real difference you'll find is over time, not immediately. HOB filters essentially do an ok job by clearing your water by removing waste and giving basic bacteria populations a chance to grow. Canister filters are built with enough filter media to develop and sustain a very stable and strong biological cycle that is less likely to be affected by changing parameters that could be encountered in a larger planted tank or overstocked aquarium.

The difference is not "clean water today" but "stable water month after month."

Noise and Appearance

Depending on where you live, a very quiet tank can sometimes matter more than it seems it should. If your tank is in a bedroom, it matters!

HOB filters make a faint trickling sound as the water returns to the tank. Canister filters, however, are virtually silent as the motor is not exposed outside the tank in a HOB type.

Also, aesthetics can matter. The canister filter's motors are enclosed, keeping them from sitting inside or on top of the tank, which gives you more room to work around in your tank and generally has a "cleaner" look.

Which One Should You Choose?

In the end, neither of the filters is a bad option. For small tanks and ease of maintenance, you can't beat the HOB filter. For large or planted tanks that will potentially have increased stocking, canister filters will maintain more stable water conditions over time.

Can You Use Both?

The answer is yes, and many hobbyists actually do prefer using both a HOB and a canister filter in combination on the same tank. A very common setup is using a canister filter for main biological filtration, and an HOB for surface agitation and supplementary filtration. It's not a necessary option for most aquariums, but it adds an extra layer of security if you plan on using a planted aquarium setup.

Common Mistakes When Choosing a Filter

Many beginners think tank size is the only factor when deciding on a filter. This is far from true. Stocking, feeding, and the amount of maintenance you're willing to put in all go into selecting the right filter for your setup. Some fish prefer not to have a strong current and may not fare well in a setup that overpowers them.

FAQ

Q1: Is a canister filter better than an HOB filter?
A1: The canister filter is more powerful and generally has better stability, the HOB is easier to manage and is usually adequate in many situations for small tanks.

Q2: Is a canister filter necessary for a small tank?
A2: The hob filter is perfectly suitable for a small tank.

Q3: What is best for planted tanks?
A3: Many planted tank systems run better using the more powerful canister filters because they create more stable conditions.

Q4: Are hob filters okay for dealing with waste?
A4: Hob filters will perform fine as long as you do not overstock your aquarium, otherwise it will likely require more frequent maintenance.

Final Thought

There's no best filter in general - only one that fits what you do with your tank. The HOB is a great option if you want simplicity. For an ecosystem that is focused on growth, consider a canister filter.