What is a Hang-On-Back (HOB) Filter?

A hang-on-back filter (HOB filter or power filter) is a self-contained unit that hangs on the rim of an aquarium. Its external placement maximizes internal tank space, making it a popular and practical choice for hobbyists in 2025.

To understand its benefits, let's first break down what a HOB filter is and how it functions.

How does a hang-on-back filter work?

A hang-on-back filter operates on a continuous cycle to clean aquarium water:

• Intake: Water is drawn from the tank through an intake tube. A pre-filter sponge can be added to protect small inhabitants like shrimp or fry.

• Filtration: Water flows through a media bay containing mechanical, biological, and chemical filter media.

• Return: Cleaned water returns to the tank via a spillway. Look for models with an overflow spillway to prevent leaks if the media becomes clogged.

Traditional vs. canister-style HOB filters

HOB filters come in two main designs, each with distinct advantages:

• Traditional HOBs: Feature a simple spillway for water return and an easily accessible media bay, ideal for quick customization.

• Canister-style HOBs: Models like the Seachem Tidal or AquaClear use modular media trays and an outlet tube. They offer a larger media capacity and a "bottom-to-top" flow for maximum filtration efficiency.

Different HOB filter designs offer unique filtration benefits.

Why Choose A Hang-On-Back Filter?

Hang-on-back (HOB) filters remain a top choice for many hobbyists, especially beginners or anyone seeking a hassle-free option. Here’s why they stand out.

Low-Maintenance, Quiet, And Customizable

One of the biggest advantages of HOB filters is their ease of maintenance. Unlike sponge filters that can release a cloud of debris when removed for cleaning, HOB media can be accessed and replaced with minimal disruption.

When set up correctly, a HOB filter can run almost silently. This is a significant improvement over air-powered systems like sponge or undergravel filters, which rely on air pumps that often generate constant background noise.

Another major benefit is media customization. HOB filters give you full control to mix and match mechanical, biological, and chemical media to suit your tank’s specific needs, unlike sponge filters which are limited to the sponge they come with.

Saves Space Inside The Tank

Most hang-on-back filter components are located outside the aquarium. This design is a huge advantage in nano tanks or smaller setups where internal space is at a premium.

By keeping the filter body external, you have more room inside the tank for aquascaping, plants, or your aquatic animals. This makes HOB filters an excellent all-around choice for many aquarium setups.

Do you even need an aquarium filter?

Yes, an aquarium filter is essential. Without one, toxic ammonia from fish waste and uneaten food builds up, which is lethal to fish.

A quality hang on back filter houses beneficial bacteria that perform the Nitrogen Cycle, converting toxic ammonia into safer compounds. A filter is not an accessory; it is the cornerstone of a stable and successful aquarium.

How to choose the best hang on back filter

Selecting the right hang on back filter requires careful consideration of several key factors to match your aquarium's specific needs.

Matching hang-on-back filters to tank size

Your filter must be compatible with your tank's volume. Heavily stocked tanks, regardless of size, have a high bioload and may require a filter rated for a larger volume to handle the waste effectively.

Understanding flow rate (GPH) for HOB filters

Flow rate, measured in Gallons Per Hour (GPH), indicates how much water the filter processes. For optimal water quality, a filter's GPH should be at least four times your tank’s volume. For example, a 20-gallon tank needs a HOB filter with a minimum GPH of 80.

A graphic illustrates the concept of Gallons Per Hour for aquariums.

GPH rating vs. actual GPH: What to look for

Manufacturer GPH ratings are based on ideal lab conditions. Real-world flow is always lower due to the filter body and media. As media clogs, the GPH decreases further. Prioritize models known for strong real-world performance over advertised GPH figures alone.

Media capacity and filtration stages

Ample media capacity is vital for aquarium stability. The best hang on back filter provides three-stage filtration:

• Mechanical: A sponge traps physical debris.

• Chemical: Activated carbon removes odors and discoloration (often optional).

• Biological: Porous media houses beneficial bacteria for the nitrogen cycle.

Noise level: Finding a quiet hang on back filter

Since filters run 24/7, noise is a key factor. To find a truly quiet hang on back filter, or even the quietest hang on back filter, consult user reviews. These offer valuable insight into a model's real-world acoustic performance.

Top hang-on-back filters by tank size

The ideal HOB filter must match your aquarium's volume to ensure efficient filtration without creating excessive current.

The best hang on back filter for a 20-gallon tank

A 20-gallon tank requires a filter with a flow rate of at least 80 GPH. The Marina Power Filter is a solid budget choice. For superior media customization, consider smaller models from the AquaClear or Fluval C-series. Adjustable flow control is highly beneficial for delicate species like bettas.

The best hang on back filter for a 55-gallon tank

A 55-gallon tank needs a filter that circulates at least 220 GPH. The Seachem Tidal 75 (250 GPH) is a top contender for the best hang on back filter for a 55-gallon tank, offering massive media capacity and a self-priming motor. The AquaClear 70 (229 GPH) is another excellent choice known for its customization potential.

Other recommended HOB filters for specific tank sizes

Beyond standard sizes, some HOB filters offer specialized features:

• Marineland Penguin BIO-Wheel: Best for high biological filtration and flow, but relies on cartridges.

• GRECH CBG-800 / AquaTop PF40-UV: Include a UV sterilizer and surface skimmer for enhanced water purification.

• Penn Plax Cascade: A versatile and affordable choice for various tank sizes.

Various HOB filters are displayed to suit different aquarium sizes.

Our top picks: Best hang-on-back filters reviewed and compared

Choosing the ideal best hang on back filter means balancing performance, features, and your specific tank requirements. Here are our top model reviews for 2025.

Seachem Tidal

The Seachem Tidal is a premium hang on back filter known for its quiet, self-priming internal motor that restarts automatically after power outages.

• Key Features: Exceptional media capacity, included Seachem Matrix biomedia, adjustable flow, surface skimmer, and a maintenance alert.

• Best for: Aquarists seeking a powerful, feature-rich, and reliable filter.

AquaClear Power Filter

A long-time favorite, the AquaClear is a reliable workhorse valued for its massive media capacity and efficient bottom-up flow design.

• Key Features: Generous filtration volume allows for extensive customization, and it includes high-quality reusable foam, carbon, and BioMax ceramic rings.

• Note: Requires manual priming and may develop a rattle over time if not maintained.

Fluval C-Series Power Filter (C4)

The Fluval C-Series offers an innovative 5-stage modular filtration system that makes maintenance exceptionally clean and easy.

• Key Features: Separate, handled compartments for each media type, adjustable flow, telescopic intake, and a pop-up cleaning indicator.

• Note: Its external motor requires manual priming.

Marineland Penguin BIO-Wheel Power Filter

This filter is distinguished by its patented BIO-Wheel, which provides highly effective wet/dry biological filtration by oxygenating beneficial bacteria.

• Key Features: Consistently high flow rate and superior biological filtration.

• Note: Relies on disposable Rite-Size cartridges, which limits customization and increases long-term cost.

Aqueon QuietFlow LED PRO Aquarium Power Filters

Designed for convenience, the Aqueon QuietFlow features a self-priming pump and an LED indicator that signals when the cartridge needs changing.

• Key Features: 5-stage filtration, high flow rates, and quiet operation.

• Note: Dependent on proprietary filter cartridges, restricting media customization.

Tetra Whisper Power Filter

The Tetra Whisper is a popular quiet hang on back filter, known for its affordability and silent operation, making it ideal for beginners.

• Key Features: Easy, no-prime setup.

• Note: Relies on disposable Bio-Bag cartridges with limited space for custom media. Build quality is less robust than premium models.

Penn Plax Cascade Hang-on Aquarium Filter

The Penn Plax Cascade offers excellent value with an adjustable flow rate and multi-stage filtration suitable for freshwater and saltwater tanks.

• Key Features: An external Bio-Falls enhances oxygenation, and it includes a reusable Bio-Sponge alongside its cartridges.

• Note: Construction materials may feel less premium.

Other Notable HOB filters

For specific needs, other hang on back filters stand out:

• Marina Power Filter: A simple, budget-friendly option for tanks up to 20 gallons.

• GRECH CBG-800 & AquaTop PF40-UV: Integrate a UV sterilizer for controlling algae and pathogens.

• Aqua-Tech Power Filter: A basic, affordable cartridge-based filter for beginners.

Advanced HOB filters integrate UV sterilizers for cleaner water.

Using and maintaining your HOB filter effectively

Proper operation and routine care of your hang on back filter are essential for maintaining pristine water and a healthy aquatic environment.

Tips for improving water clarity with your HOB filter

For crystal-clear water, ensure a turnover rate of 3-4 times your tank's volume per hour. Using fine filter floss will trap tiny particles. Be aware that some hardscapes, like certain woods, can release debris that clouds water and clogs filters.

Managing flow for bettas, shrimp, or planted tanks

Use the adjustable flow control on your HOB filter to create a gentle current for delicate species like bettas. It's better to choose an appropriately sized filter for your tank than to excessively restrict the flow on an oversized unit, which can compromise filtration.

Are hang-on-back filters noisy? Addressing common concerns

Noise from a hang on back filter usually has a simple fix:

• Rattling or Humming: This typically means the impeller is dirty. Clean it with a soft brush.

• Splashing: This occurs when the water level drops. Keep your tank topped off to maintain a quiet hang on back filter.

What maintenance does a hang-on-back filter need?

Routine maintenance is simple, especially with custom media:

• Every 1-4 weeks: Rinse or replace the mechanical filter floss/pad.

• Once a month: Gently rinse the biological media (sponges, ceramic rings) in old tank water to preserve beneficial bacteria.

• Occasionally: Clean the impeller and intake tube to ensure optimal flow.

What happens during a power cut with your HOB filter?

A filter's ability to restart after a power outage depends on its motor:

• Internal Motors (e.g., Seachem Tidal): These are self-priming and will restart automatically.

• External Motors: These may lose their siphon and require you to manually refill the filter box with water to restart.

Frequently asked questions about HOB filters

Can I use a HOB filter for saltwater aquariums?

Yes, HOB filters are suitable for smaller nano reef setups. For best results, customize the media with live rock rubble or convert the media chamber into a mini-refugium.

How can I make my hang on back filter quieter?

To ensure a quiet hang on back filter, keep the aquarium water level high to eliminate splashing. Regularly cleaning the impeller will prevent rattling sounds, helping you achieve the quietest hang on back filter operation.

A high water level minimizes noise from your hang on back filter.

Are there hang on back filters suitable for bettas or shrimp?

Yes. Look for models with an adjustable flow rate to prevent strong currents. It is also highly recommended to add a pre-filter sponge over the intake tube to protect them from being pulled in.

Choosing the best hang on back filter is key to a healthy aquarium. By matching GPH to your tank size, opting for customizable media over cartridges, and performing regular maintenance, you ensure optimal water quality. Backed by 20 years of experience, Betta USA Aquatic is dedicated to helping you create a thriving aquatic ecosystem.

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