How Does A Hang On Back Filter Work? Models, Setup, And More

    How Does A Hang On Back Filter Work?

    Aquarium filter technology comes in a number of designs. But the most popular is by far the hang-on-the-back filter. They are great at providing crystal-clear water and removing dissolved pollutants. But just how does a hang on back filter work? And is it right for your aquarium?

    Hang on back filters provide all three of the essential filtration methods; chemical, mechanical, and biological filtration. They are easier to access and faster to maintain than canister filters. They also provide good aeration and water turnover.

    In short, hang-on-back filters are popular for very good reasons!

    What Is A Hang On Back Filter?

    What is a hang on back filter

    The filtration system is the life support system for a fish tank. Without it, clean water will become polluted as fish waste accumulates. Leftover food and poop decay into ammonia. Which can stress and eventually kill your pet fish.

    Filters are a major line of defense for aquarium fish health. They pull out this organic debris, processing it through several layers of filter media. Clean water is then sent back into your aquarium!

    There are other kinds of tank technology that can purify your water. Protein skimmers, ultraviolet clarifiers, and a sump filter all have their place. Especially on marine coral reef tanks and other setups with demanding pets. But hang-on-back filters can be a part of any kind of aquarium system where a filter is needed!

    Hang on back filters (also called power filters) are some of the most recognizable types of filters in the hobby. They get their name because most designs are meant to be attached to the rim of the fish tank.

    Most aquarists choose to place their power filters along the rear of the tank. That way the unit is not so visible compared to the front or sides of the aquarium. But there’s no reason why you couldn’t place it elsewhere.

    In fact, placing an hob filter on the side of a tank is a good idea if the water flow is especially strong. That way the flow will be dissipated along the entire length of the tank!

    Do you happen to be more of a visual learner? Then take a moment to watch this video. It breaks down the points I’ve made here on hang-on-back filters in great detail:

    YouTube player

    How Does A Hang On Back Filter Work?

    How does a hang on back filter work

    Hang-on-back filters work similarly to other types of filters. They provide three kinds of water purification: mechanical, biological, and chemical filtration.

    Mechanical Filtration

    Mechanical filtration is the simplest form. It is when an aquarist uses filter media that physically screens particles from the water. Cotton floss is the most common form of mechanical filtration. But you can also use diatomaceous earth, which is fine enough to scrub even green water aquarium algae from your water.

    Chemical Filtration

    Chemical filtration takes things a step further. Dissolved organic molecules like proteins and amino acids are adsorbed or enter into chemical reactions with the media. Activated carbon is what most hob filters use. But some of the more customizable designs have space for more specialized kinds of chemical filtration!

    Biological Filtration

    Last comes biological filtration. This is achieved through the actions of your beneficial bacteria. They are a critical part of the aquarium nitrogen cycle. Fish waste and leftover protein decay into ammonia naturally.

    Ammonia (NH3+) is highly toxic to fish health. Fortunately, there are bacteria that find it delicious. They consume this ammonia, excreting it as nitrite (NO2-). Nitrite is a little less toxic than ammonia. But still not too good for fish.

    That’s where the second set of good bacteria come in. They feed on nitrite, reducing it further into nitrate (NO3-). Nitrate is well tolerated by fish and remains in the water until you remove it through water changes. Or live aquatic plants consume it as fertilizer.

    All of the best hang-on-back filters have loads of surface area inside. Generally, they use plastic mesh, ceramic bio balls, or other additions. Which ensures that your beneficial bacteria have a place to live. Polishing ammonia and nitrite from the system for you!

    Best Hang On Back Filter Models

    Best hang on back filter models

    Hang-on-on-back filters come in endless sizes and models for keeping fish alive. But these four are the best hob filters for the average aquarist!

    Tetra Whisper IQ Power Filter for Aquariums, with Quiet Technology

    New aquarists often try to balance effectiveness with affordability when choosing filters for smaller tanks. But the Tetra Whisper lineup proves that you don’t have to!

    Their Whisper IQ line of power filters has been in production for decades. Tetra pioneered quiet operating magnetic impeller-driven pumps. So you can use their power filter even in the bedrooms of children and other noise-sensitive locations.

    Each filter uses a cotton and carbon cartridge. Making biweekly maintenance a breeze! Biological filtration occurs in a secondary chamber with extra surface area for bacteria to grow on. Ensuring ammonia levels are well controlled for your fish!

    Aqueon QuietFlow LED PRO Aquarium Power Filter

    The Aqueon QuietFlow LED PRO are excellent hob filters for intermediate to advanced-level hobbyists. While not as quiet as the Whisper IQ line the pumps are still usable in most settings.

    One element that sets the Aqueon line apart is the LED light built into it. Rather than lighting your fish tank, it’s part of a monitoring system for water flow. When the filter requires maintenance, flow is reduced. Causing the LED to light up.

    The Aqueon QuietFlow also includes an internal filter cartridge. And it provides all three types of filtration so tank water is purified before exiting the unit.

    Marineland Penguin Bio-Wheel Power Filter

    Marineland Penguin were the first to pioneer the use of bio wheels in filters. Bio wheels serve two functions. They first add extra aeration to the outgoing water. But their main purpose is to provide even more living space for beneficial bacteria to grow.

    The biological filtration provided by the wheels is a tradeoff since noise is increased by all of that splashing. But they are one of the best filters for nitrogenous waste control; as good as a canister filter of the same size!

    AquaClear Fish Tank Filter

    AquaClear fish tank filters are very good filters. In fact, they are the brand I usually go with on my standard aquariums.

    I prefer using an AquaClear hob filter because the media chamber is designed to use any media you want. Foam inserts, bio balls, lava rock, activated carbon…You aren’t trapped in using a proprietary media choice, as most cartridges are.

    You do need to keep up with regular maintenance. Otherwise, the unit will start bypassing water around clogged media. But the clear plastic design ensures that you can see when your filter media is starting to get dirty.

    How To Set Up A Hang On Back Filter

    How to set up a hang on back filter

    Setting up a hang on back filter need not be a complicated task. And once the unit is running they need little attention from you, besides biweekly cartridge changing!

    Step 1:

    Remove the hang-on-back filter from the box. As well as any included media and instructions. Rinse the activated carbon before using it. Carbon is full of dust that can irritate fish gills if added to a filter when dry.

    Step 2:

    Add the filter media to the chambers in the order the instructions tell you to. This is important because different filters take in water from different directions. Some send it from the back to front, while others might come from below. Not adding media in the right order may cause it to not work properly.

    Step 3:

    Partially fill the hob filter with aquarium water before turning the unit on. Some filters will self-prime. Others need some water to get started. If you try running a non-primed filter without water the pump may overheat. This could permanently destroy the motor since they rely on water to keep cool.

    Step 4:

    As water fills the filter, it may grind and grumble a bit, but this is normal. Water should then cascade from the outflow into the aquarium. Watch the running water for a few minutes to make sure the unit is operating normally. Make adjustments as needed using the flow control that many units have.

    Step 5:

    Every two weeks, check the filter to see if any of the media needs changing. Chemical media does not last forever. Mechanical media also needs to be either cleaned or replaced. Biological filtration media does not usually need replacing. But if the growth of bacteria is too thick, you can rinse away some of it using aquarium water.

    Pros And Cons Of Hang On Back Filters

    Hang-on-back filters are a great solution for most fish owners. But like everything, there are pros and cons. Here are each of those points outlined for you!

    Hang On Back Filter Pros

    Here are the main pros of using hang-on-back filters:

    • Ease Of Setup, Access, And Maintenance: people love to buy hob filters because they are easy to set up, access, and maintain. You can have a new power filter up and running in just a few minutes. There are few moving parts to fuss with. If you need to access it, it’s right on the side of your tank. And cleaning the filter usually just means removing one cartridge and replacing it with another!
    • Very Affordable To Buy and Maintain: hob filters offer the most bang for your buck when it comes to purifying your aquarium water. A canister filter might be able to do a better job, in certain situations. But you’ll also be paying more, for a less easy-to-manage unit.
    • Great For All Tank Sizes: a canister filter is ideal for larger tanks. Sponge filter models work great for small setups. But you can use a hang-on-the-back model as an aquarium filter for any sized tank! They have flow rates, media chambers, and additional features that are sized specifically for the aquarium you have.

    Hang On Back Filter Cons

    As great as hang-on-back filters are, they do come with a few cons:

    • Not Super Customizable: power filters do offer some customizability. The larger the unit is, the more space it offers for you to add your own preferred media. But canister filters are much better at this. Hang-on-back filters will sometimes allow water to bypass them if you don’t add your custom media with care.
    • Often Use Proprietary Filter Media: on the one hand, it’s always easy to find replacement cartridges for a power filter. Aquarium technology producers make them in multi-packs so you don’t have to take frequent trips to the pet store. Something to think about is that the cost of these carbon cartridges is usually higher than it is refilling them yourself. Yet even if you wanted to use your own cartridges, you probably won’t be able to. The design of many hang-on-back filters is set up so that you have to use the company’s filter cartridge. The costs aren’t crazy high but they can add up.

    Hang On Back Filter Versus Other Filters

    Now you better understand what hang-on-back filters are. As well as their main benefits. But how do they compare to the other types of filters out there?

    Hang On Back HOB Versus Canister Filters

    Canister filters are the aquarium filters that are the stiffest competition for an hob filter. They offer all three types of filtration. Yet canister filters also come in larger sizes, as well as designs that prevent bypassing through a crowded media chamber.

    One major difference between the two is the ease of access. Canister filters are usually placed under the tank so they don’t take up visual real estate in the room.

    To swap out old filter media you need to disconnect it from the hoses running to the tank. Lift the canister filter out from under the stand. Open it. And usually, remove several other media chambers before getting to the one you want. It’s time-consuming and often messy compared to maintenance on most hob filters.

    The flip side is that the filter box of a canister filter is much more spacious. You don’t have to work around a proprietary filter cartridge as you do with hob filters.

    Hang On Back HOB Filters Versus Sponge Filter

    HOB filters offer a number of benefits compared to a sponge filter. Sponge filters offer primarily mechanical filtration using their sponge block. However, the huge surface area they have inside provides a fine home for beneficial bacteria colonies.

    Some sponge filter models also have cartridges for chemical filtration media. Though not nearly as much as an hob filter or canister filter. A sponge filter will be cheaper and often quieter since it runs on a single air pump.

    That said, the use cases are pretty different. I only recommend sponge filters for aquariums where you only need a little filtration. And you need a gentle current.

    They are excellent for fry-rearing tanks and shrimp aquariums. Baby fish and shrimp would get sucked up by even a small hob filter. But a sponge filter won’t trap or kill them.

    You might also use a sponge filter on a betta tank, quarantine tank, or another small setup. But for any other aquarium, an hob filter will do a much better job of maintaining good water quality. The flow rate (which improves oxygenation and heat exchange) is also much higher!

    Hang On Back Filters Versus Undergravel Filters

    This comparison is the starkest of the three because undergravel filters work in very different ways. Undergravel filters use your aquarium substrate as mechanical filters. Water flow is directed from the top of the gravel down. Screening floating particles from it.

    The gravel bed is also a hot place for beneficial bacteria to live. But undergravel filters provide no chemical filtration. And the flow rate is lower compared to hob filters or canister filters.

    Undergravel filters are also very messy to clean. The debris does not decay quickly. And if you lift the plates to clean under them, gunk immediately spreads into the rest of the fish tank.

    I only recommend using an undergravel filter on a planted aquarium. Live plants can thread their roots down into the substrate. Using the muck as fertilizer for their growth, so you don’t have to clean under the undergravel filter at all!


    Hang-on-back filters are a good choice for any kind of aquarium. Freshwater or saltwater, large or small…Their technology is suitable for aquarists of all skill levels as well.

    Canister filters may hold more media and offer greater potential for customization. But they take more time to maintain, as well. They will also look less attractive unless you can hide them under an aquarium stand.

    Sponge filters are cheaper but also less effective. Especially when you want stronger water flow and a good source of chemical filtration. Plus they take up a lot of visual real estate inside the fish tank.

    Hang-on-back filters are the best balance in terms of price, ease of use, and technology for most aquariums and fish keepers!

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