betta fish tank filter

The 5 Best Filters Options for a 5-Gallon Betta Fish Tank Compared

While the 5 gallon fish tank is a small one, proper filtration is still an important part of the equation. Waste and impurities can build up quickly in a small fish tank. This is even more so when you’re working with delicate fish like bettas. While bettas are one of the more popular fish for beginners, they still require proper care and attention to ensure their tank keeps them healthy and safe. We wrote this article to help you find the best 5 gallon betta fish tank filter.

best 5 gallon betta fish tank filter

But how do you know which filter is the
best one for your betta fish tank?

In this article we’ll take a closer look at why filters are important even for small betta tanks and we’ll also review out top-5 best aquarium filters for small fish tanks. We hope this guide will help you choose the solution that is right for you, your tank, and your betta.

The Best 5 Gallon Betta Fish Tank Filters Compared

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The Best 5 Gallon Betta Fish Tank Filters Reviewed

In this section, we’ll review five products to help you choose the best filter options for your 5-gallon betta fish tank.

- 1- Luffy Marimo Moss Ball

If you’re looking for something that has the benefit of being a living plant, a biological filtration device, a toy for your betta, as well as an adorable low-maintenance aquarium ornament, then the Marimo Moss Ball is a great option to consider. This is our top-pick for a 5 gallon betta fish tank filter

Not only are these moss balls are a gorgeous tank ornament, but they are also live plants that absorb nitrates from your tank, including phosphate and ammonia. And given that they’re a living plant, they also help oxygenate the water. If you have a 5 gallon tank or smaller, adding some of these balls can be a great way to help keep the water fresh without needing to use a mechanical or power filter.

They come in many sizes ranging from “nano” (about the size of an M&M) to “giant” (about the size of a tennis ball). Marimo Moss Balls are also completely natural and eco-friendly. The best varieties aren’t dyed or painted – it’s 100% natural moss. That means they’re safe to put in your tank. Given that they're a living plant they will need light and freshwater to survive.

Given that these are living plants, it also means that you need to be careful when ordering these. Take care not to order when it is extremely cold or hot outside. You also should not delay in opening up the box and putting it in your tank when you get it.

When you do get it you should give it a gentle wash before putting it in your aquarium. You should also rotate them regularly so that they don’t develop brown “pressure” spots from always sitting in the same place.

As Marimo Moss Balls are a natural item, they aren’t always as perfectly spherical as they might appear in photos. They also can have small brown spots on the surface. Don’t be disappointed if this is how yours look. In fact, you should watch out for moss balls that are perfectly round and lush green all over, as these could be artificial or enriched with chemicals.

Marimo Moss Balls have the added advantage of helping to reduce algae growth in your tank. They like to eat the same nutrients as algae and by absorbing the available nitrates, phosphates and ammonia in the water they inhibit the growth of any competing algae. They’re also snail-proof and won’t get eaten up.

Last but certainly not least, most bettas love to move things around as part of their natural behavior. You betta may nose around your moss balls, lie in their shade, and snuggle up against their sides. It’s wonderful to see bettas expressing their natural habits around a Marimo Moss Ball.

Like everything though, there’s no guarantee – you might find your bettas completely ignore it! But at least when you’re adding a moss ball you’re also enriching the environment of your aquarium by providing opportunities for play and stimulation.

- 2 - Aqueon QuietFlow E Internal Power Filter 10

For a quiet mechanical filter that does the job quickly and effectively, the Aqueon Quietflow E Internal Power Filter 10 can be a good choice. This filter is a jack-of-all-trades as it features mechanical, chemical and biological filtration. It uses:

  • Chemical filtration – via a carbon cartridge that takes care of odors and discoloration
  • Biological filtration – through a bioholster that removes ammonia and nitrates
  • Mechanical filtration – with a coarse media sponge that collects particles and debris.

A word of warning before we go any further though - this filter has a higher flow rate than other products. Make sure you consider the 10-100g model or choose the mini “10” version so that you don’t accidentally end up with a filter designed for a 50 - 400 gallon tank! You can also manually adjust the flow rate, even on the mini model, so that your bettas aren’t being spun around in the tank. This article discusses ways to effectively reduce the flow rate of a filter.

This filter has an auto-start pump that doesn’t need any priming, and even better, it will automatically restart if the power is interrupted and then restored. If you’re going away on holiday, for example, a filter like this can help you to relax knowing that a temporary power outage won’t affect the filtration in your tank.

The filter uses Aqueon replacement filter cartridges in the small size, which can be easily found and purchased on Amazon.

- 3 - AquaClear Power Filter 110 V

Another good filter option for your 5-gallon betta tank is the AquaClear Power Filter 110V, in the 5-20 gallon model. This filter has a gentle water flow, so your bettas can swim around calmly and safely. It’s quiet and sits on the outside of the tank using a hang-on-back system, so it doesn’t take up valuable space inside.

The AquaClear Power Filter uses continuous biological filtration via foam and carbon BioMax filter inserts. This preserves healthy bacteria in your tank while removing toxic chemicals such as ammonia and nitrates. Because you’re never throwing away a cartridge, you keep all the beneficial bacteria in place and doing their job. This ensures a good continuity to your water environment as the filter doesn’t need to re-colonize.

The filter has three media inside it:

  • A foam insert on the bottom, which removes debris and distributes water effectively. It also provides biological filtration
  • An activated carbon filter insert in the middle, with a large surface area that adsorbs impurities and toxins
  • A special BioMax ceramic ring on the top level, which has a complex pore system designed to help healthy bacteria grow and thrive.

Be aware that this is a high-maintenance filter, and expenses can add up. It’s recommended that you clean this filter at least every two weeks, and replace the carbon inserts every month, the foam inserts every other month, and the BioMax insert every third month.

- 4 - Bacto Surge High Density Foam Filter

If you’re looking for a filter that won’t make any noise at all, a standard foam filter can be a good choice. The Bacto Surge High Density Foam Filter is a small mechanical/biological filter that works well in tiny tanks and small aquariums.

Healthy bacteria live on the foam and process chemicals and other nasties out of the tank water. Because it doesn’t pump any water there’s no current to stress your fish – just a delightful stream of bubbles. At 5" x 5" x 6", it’s a little chunky and not necessarily the most attractive feature to add to your fish tank.

The filter has a weighted bottom, so it will sit where you put it. But if you find that it’s floating, just squeeze it so that it fully absorbs the water and it will sink back down.

Sponge filters do need regular cleaning, at least every week to 10 days, especially in a small tank. Cleaning your filter is a simple process – you just need to use your existing aquarium water to wash the muck off the sponge. Never use hot water, tap water or distilled water!
You want to keep the healthy bacteria on the sponge and not kill them.

- 5 - Penn Plax Small World Aquarium Filter & Air Pump

It can be challenging to find a filter that’s specially designed for a small 5 gallon aquarium, but that’s where the Penn Plax World Aquarium Filter comes in. Extremely small and inexpensive, the Penn Plax World Aquarium Filter uses a disposable cartridge that combines carbon and zeolite for chemical filtration, along with a sponge that provides biological filtration. The zeolite crystals take care of the ammonia in your tank and the activated carbon stops harmful gases and odors. The filter comes with a bracket and suction cups to attach to your aquarium wall.

While the manufacturer advertises these for up to 5-gallon tanks, we find that these filters work best for tanks 3 gallons and less. Thus, it might be best to use this in combination with another filtration method – for example, an undergravel filter or a few moss balls – or you could also try a stronger air pump to increase the water flow. You can also pop two in as they’re so tiny.

The cartridge in this filter needs changing regularly given that it’s a small filter and it gets filled up quickly as a result. This means you will have to stay on top of your cleaning and replacements so that your tank stays healthy, fresh and clean.

Why are filters important for small fish tanks?

Although it’s technically possible for fish to thrive in a small aquarium without a filter, it can be hard to keep a tank properly clean without one. Especially small 5-gallon tanks that become dirty and stagnant much more quickly than larger tanks.

Filters perform an important function – they remove waste and debris from water. This includes things like old food, fish waste, decaying organic matter from plants, dust and any other free-floating particulates, and chemicals that can become dangerous for your pets. While it’s important to get rid of all of this stuff, it’s particularly critical in the case of fish waste.

Excreta is your fish’s natural way of cleaning their internal systems and removing toxins. But where do those toxins go after your fish have gotten rid of them? Straight into the water inside their tank...

In a natural environment, this waste would normally be heavily diluted and swept away on a current or eaten up by healthy bacteria. However, things are different in your tank where the water levels are much lower – and there’s no natural current to wash everything away. If fish waste isn’t removed regularly and thoroughly, it can build up and become concentrated in the water. This can poison or even kill your fish.

The early stage of this process is called ammonia stress or nitrogen stress. If you don’t take steps to correct it immediately, it can tip the balance and turn into ammonia poisoning, which is also known as nitrogen poisoning.

What kind of filter can you use in your 5 gallon fish tank?

Broadly, there are three common types of filters you can look at using in your tank – usually in some kind of combination.

  • Mechanical

  • Biological

  • Chemical


Mechanical filtration works by physically trapping the debris in your aquarium. Mechanical filters use a “medium” to strain the water and catch this material – often it’s a sponge, pad, floss or other kind of material that’s placed inside a filter casing and provides biological filtration.

Sponges, pads and blocks for mechanical filters (usually power filters and canister filters) come in a range of shapes, sizes and densities. Make sure you choose one with the proper pore size – a pore size that’s too fine will clog very quickly, and a pore size that’s too large won’t trap what it needs to.

You can also look into filter floss or filter wool for your filter. The rate of water flow through a mechanical filter is the key element in keeping your aquarium happy and healthy. If the water flow is too fast or slow, it will negatively impact the filtering capacity. Manufacturers tend to set the flow rates, but be aware that your tank might need a different rate of flow.

Mechanical filters need to be removed, cleaned, and replaced on a regular basis. Otherwise the trapped material will build up and decompose back into your aquarium, and the healthy bacterial colonies in your media will die off - which defeats the whole point of having a filter in the first place.

Do Small Betta fish Tanks Need A Mechanical Filter?

Bettas are delicate fish and they don’t do well in water that has a strong current. So is it overkill to use a mechanical filter in a 5-gallon tank? There are two schools of thought on this:

  • For

    Mechanical filters keep tanks clean and help to provide a healthy environment. They’re used for other fish, so why not for a betta too? It can be hard to keep up with regular water changes in such a small tank – and mechanical filters can provide security if you need to go away for work or holidays.

  • Against

    Bettas like calm water with little or no current. Some bettas have long tails or large fins that can catch a water current and act like a sail – this can cause stress and fin damage. A mechanical filter isn’t essential – you can do regular water changes and use other methods to keep the water clean. By using one you could put your delicate fish at risk.

It’s easy to see both sides of the argument here. Ultimately, you need to consider your own aquarium and situation and make the decision that is best for you and your betta.


Biological filters use living organisms to help your fish tank break down waste naturally. These can include plants as well as small invertebrates. As long as there are a number of places for micro-organisms to grow, a biological system can be a natural and effective choice.

To begin with, you might choose a mechanical filter, which usually combines carbon with a bio filtration medium – this is what the healthy bacteria grow on. This medium usually looks like blue floss but it could also be a sponge or a rubber pad.

Gravel is another critical element of your biological filter system. Gravel provides a large surface area for your micro-organisms to flourish in. You must take care of your gravel by allowing it to grow its colonies of bacteria for about 2 weeks before you add any fish. Thins means you should only have water, gravel, and maybe a few plants in your tank for the first couple weeks.

Once your tank has established itself you can add 2 or 3 fish and them establish themselves for a few weeks. Then, if you want, and you have space, you can add some more. This helps the micro-organisms grow strongly without being overcome by waste.

Make sure you clean your gravel properly during water changes. Use a gravel vacuum: we suggest trying the TERA PUMP Aquarium Gravel and Sand Cleaner, which is available on Amazon.

Plants are also an important part of your bio-filtration system. Some aquarists like to cultivate a special algae wall, but a more attractive option is to choose from the wide variety of potted, rooted or free-floating plants that you can add to your aquarium. Make sure you choose plants that suit the kind of fish you plan to stock, as well as the heaviness and size of the gravel you have added.

Lastly, you can also choose to add a range of invertebrates, live rock, or live sand. If you want to add some invertebrates such as shrimps or snails, make sure they are compatible with Betta Fish. Here is a list of 10 fish and intertebrates that can live with Bettas. Adding some snails or crustaceans like redclaw crabs brings also some benefits when it comes to algae control. These kinds of animals need special diets and care schedules, so make sure you do your homework so that you can look after them properly.


Chemical filtration refers to a process that uses activated carbon, resin, or other adsorbent materials to get rid of dissolved particulates in your aquarium. Adsorbent means that matter sticks to the surface of the carbon or resin rather than soaking into it. Activated carbon is full of millions of tiny holes or “pores” – these act as little pockets that collect dissolved material.

The chemical filtration process can remove chemicals like copper and chlorine, as well as dissolved proteins and carbohydrates like those found in fish food and waste. However, once all of the pores in your chemical filtration system are filled up, the carbon isn’t effective anymore and it will start to act as a biological filter instead as bacteria land on the surface to eat up the material.

However, beware that carbon can absorb many tank medications as well, especially antibiotics. You should probably remove any carbon before adding antibiotics to the water. Just remember to put it back after the treatment period has finished.

Resins are less popular than carbon, but they can still be an effective choice. They attract a special molecule such as ammonia or nitrate. Resin can help to strengthen the filtering ability of carbon, so they’re often used together.

How to choose a filter for a 5 gallon betta tank

Ultimately you need to choose a filter based on your aquarium and the kind of betta you will stock in it. You should consider these points when selecting a filter:

  • Flow Rate

    Bettas tend to do best with gentle, low, or no flow filtration. If you’re thinking about a mechanical filter or internal filter with a pump, make sure you choose one that has a slow flow rate or a rate that you can change. If you’re stocking delicate varieties, like those with long tails such as the half-moon betta, then it would be better to have no movement in the water at all.

  • Easy to Clean

    A cartridge system that’s easy to remove and clean or replace is great because you'll need to do it regularly

  • Filtration Media

    The type of filtration media used can have a big impact. Sometimes having all three methods of filtration can give you the best water quality for your tank. In other cases – for example if you want a planted tank – just one or two might be better.

  • Reliability

    Will it continue to perform well over time? Or will it clog up or break down? What happens if the power goes out while you’re away? Talk to other fish owners to understand their experiences and read up about the kind of filter you’re considering.

You can also build your own filter – here’s a short video that shows you how.

Key things to watch out for in a 5 gallon betta tank filter

The first thing to watch out for is how clean your filter is. If you’re not regularly removing your filter media and cleaning it, then debris will build up and begin decomposing, which means your filter won't be working properly.

The second thing to watch out for is how clean your filter is. Get the point? It's very important to clean your filter regularly. We cannot stress this enough.

The third thing to watch out for is current flow. Your fragile little betta might be fighting a current that you thought was fine – remember to check for distress and adjust if necessary.


As we’ve said, when it comes to filtration, the best filter is the one that works for you, your bettas, your tank, and your individual circumstances. Biological, chemical, mechanical or a combination of all three – it’s up to you.

If we were putting together a new 5-gallon tank for bettas, then the Marimo Moss Balls would be our first pick for filtration. Because Marimo Moss Balls come in a range of different sizes, you can add as many or as few as you like. They don’t need a lot of care beyond occasional rotation (and you might find your betta does that for you), and they’re inexpensive and easily replaced. There’s also no worrying about current, water flow, or noise with a moss ball.

This option packs a powerful punch – it’s hard to pass up something that is not just a biological filter but also an eco-friendly, living plant that adds to the decor of your tank while also inhibiting algae. Moss balls are also snail-friendly and a stimulating toy for your fish.

The 5 Best Filters Options for a 5-Gallon Betta Fish Tank Compared