Fish Tank Filters: Which One Should You Get?

What are people thinking when they hear that you have pet fish? They probably conjure up memories of their great aunt’s dirty goldfish tank, covered in mystery slime and reeking of stagnant swamp water. But you and I know the secret to having a beautiful aquarium with crystal clear water… clearly, we just need to find the perfect fish tank filter!

Why do Aquariums Need Filtration?

As one of the key components of an aquarium, filtration is responsible for moving and cleaning the tank water, making it safe for fish to live in. The three main types of filtration are mechanical, biological, and chemical filtration. There are some filters that work better than others, so let’s take a look at each type.

Mechanical filtering uses sponges and filter socks. Filter floss pads are used to physically strain out any debris in the water. This is similar to a coffee filter. Mechanical filtration works as a garbage container that collects trash. As such, you, as the fish owner must still clean the filter media. – Biological filtration uses beneficial bacteria or aquarium plants that can consume the toxic ammonia and nitrogen compounds that result from your fish’s waste. Beneficial bacteria grows on any surface, including the walls and gravel in your aquarium, so many filters come with biomedia or bio-rings with high surface area to provide more places for the bacteria to live. – Chemical Filtration uses activated Carbon or special resins that can remove medication, tannins, as well as other impurities. The media can no longer absorb pollutants from water once the chemical filtration has become saturated with impurities.

There are many types of filter media: biological, mechanical and chemical.

Bottom Line: mechanical filtration makes your water clearer, biological filtration makes your water safer, and chemical filtration is something best saved for removing impurities from the water.

What Are the Most Popular Types of Filters?

Now that you’re familiar with what filtration does for an aquarium, let’s talk about the actual equipment you can purchase (in rough order of most to least common).

Sponge Filter

Aquarium Co-Op sponge filters

This filter is the most basic. It requires at minimum three components: a sponge filtre (which sits within the tank), an air pump (which sits out of the tank), and airline tubing that connects them. The sponge filter is hollowed by air pumps that push air through the tubing. The rising bubbles of air draw water through the sponge walls, thus mechanically collecting debris from the water and giving beneficial bacteria place to grow.

Advantages: There are many pros to this device. It is easy to use, cheap, and durable. It allows for good water circulation and surface stirring, but is gentle enough not to eat shrimp or fish fry. Plus, during power outages, the beneficial bacteria on the sponge stays in the oxygenated tank water (which gives it a longer chance of surviving), and you can even purchase battery-operated air pumps to prepare for emergencies.

Cons: The sponge filter takes up physical space in the fish tank, so you may want to hide it behind a rock, plants, or other aquarium decor. You can’t add chemical filtration to the sponge filter. The bubbling sound that a sponge filter makes is not something I like, but it can be fixed by using a little bit of air stone.

Summary: Spongefilters are often found in fish shops, fish room, and breeding areas because they are so reliable and affordable. Use what’s proven to work.

Hang On-Back Filter

Hanging-on-back filter to nano tanks

Just as the name describes, a hang-on-back filter sits on the top rim of an aquarium with the filter box hanging outside the tank and the intake tube lowered into the tank. Water is sucked up the intake tube via the filter’s motor, passed through all the media in the filter box, and then typically returned back into the aquarium like a mini waterfall.

Pros: I love how customizable the filter media is and the fact you can include all three types of filtration. A hang-on-back filter performs better than a sponge filter at mechanical filtration. You can also add a fine filter pad for extra polishing. The device is very simple to service since most of the media is outside of the aquarium, allowing you to easily remove the media for gentle washing. AquaClear filters have adjustable flow rates, which allows me to control the water circulation.

Cons Additionally, if you don’t like the waterfall sound, just raise the water level in your aquarium and you’ll barely notice the noise.

Bottom Line: This is the first filter I ever purchased and it’s still in use today for good reason. As a popular staple in the freshwater aquarium hobby, the hang-on-back filter excels in all three arenas of filtration and has extremely flexible options for hot-rodding it to your tastes.

Canister Filter

A canister filter is essentially filtration in a plastic cylinder or box form factor that often sits under the tank, with intake and output hoses that reach into the aquarium. With the aid of a motor, water is drawn into the canister, travels through several trays of filter media, and then is returned to the fish tank.

Pros: Just like the hang-on-back filter, the canister filter takes up very little room inside the aquarium and is highly customizable. Some models include extra features such as an inline heating, UV sterilizer, or automatic priming. Many hobbyists consider it to be one of the best readymade filters on the market.

Cons This handy little canister is difficult to service. It requires you to literally disassemble the entire setup each time you need to clean it out. Keep your towels handy as there is a higher chance of flooding during maintenance. Finally, because the filter media lives outside the aquarium in a closed box, there’s a greater risk of suffocating and killing off your beneficial bacteria during a power outage.

Summary: If your discus needs extremely clean water or you have an African cichlid aquarium with high bioloads, then this might be the right product for you. Just be prepared to spend the extra money and time it takes to own this premium product.

Fluidized Bed Filter

Ziss moving bed filter, powered by an air pump

Fluidized bed filters are more DIY-oriented than they were in the past. However, there is now a small, easy-to-use Ziss bubble Moving Media Filter. Water flows into a chamber of small media granules (like sand or plastic pellets), causing the media to swirl about like a fluid. This constant churning greatly enhances bacteria growth from the media’s constant contact with oxygenated water.

Advantages: Because the Ziss filter works in the same way as a sponge filter but is air-driven, it doesn’t have any mechanical parts to break. It also provides a lot of surface agitation which allows for greater gas exchange. The filter comes with a sponge bottom prefilter that prevents fry getting trapped and is easy to take out for cleaning. As a device focused on biological filtration, it’s great for goldfish and turtle aquariums with high bioloads – and unlike sponge filters, the hard plastic is too hard for turtles to chomp through!

Cons: This filter is relatively tall at 11 inches, so it’s only suitable for taller tanks (not a 10 gallon or 20 gallon long aquarium). It is not as easily customizable to add chemical filtration or mechanical filtration, like the sponge filter. The noise level is comparable to that of a sponge filter, mainly due to the bubbles and pump.

Summary: To improve biological filtration, a fluidized-bed filter may be a good option. One Ziss Bubble Bio filter holds 20-40 gallons water. It can be used alone or with another filter.

Live Aquarium Plants

Which filter should I choose?

Ah, the golden question every aquarist always wants to know. First, I haven’t covered all the filters. Second, there is no “best” filter that fits all. There are many different tools that can accomplish different tasks. Consider the needs of your aquarium – such as your stocking levels, water circulation, ease of use, and budget – and pick the solution that works for you. Good luck and happy filter shopping!