Best filters for small fish tank – Detailed reviews & Buying guides

Owning a small fish is a difficult task for any aquarist because there will be many challenges ahead of your small water life, especially in maintenance and how to monitor and keep your water crystal clear. Thus, choosing a good filter for your small fish tank (any tank which is smaller than 10 gallons) should be the first priority on the checklist. Let’s have a look at some of the best filters for small fish tank that we have helped you to seize out of the current market. 



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Best filters for small fish tank [Updated 2021] 

Top 1:  NO.17 Submersible Aquarium Internal Filter

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This filter is suitable for the aquarium holding from 1 – 10 gallons with a maximum flow rate of 132 GPH. Item dimensions: 10.87 x 3.07 x 1.97 inches.


  • Adjustable flow rate: The maximum flow rate is very powerful – 132 GPH means that it could filter a 33-gallon tank in 4 hours. However, it is adjustable so that you could choose the suitable flow rate up to your tank size and needs. It runs with only 6 wattages, which is equal to a medium LED bulb, and helps you to save more energy and avoid heating up your tank.
  • Compact design: This submersible filter is very easy to hide with its sleek and neat design, which will not steal away your good view of the tank. The multi-stage filtration media assure to keep the tank water crystal clear and it is also reusable. The pump intake is equipped with the filter net so that the pump will not be clogged with unexpected things, even your small fishes.
  • Quiet operation: I must say the No. 17 has used a very high-quality motor for this product because I hardly hear any sound from this filter in my 5-gallon tank.
  • Easy-to-assemble and clean: The package came with an assembled filter, however, when you disassemble it for cleaning every 2 months as recommended by the manufacturer, it is also very easy.


  • This filter does not have a replacement cartridge and does not have charcoal. Thus, it depends mainly on mechanical and biological filtration. Your task is to review water quality daily and do the cleaning job when the sound of the motor is bigger.

Top 2: Tetra Whisper Internal Filter for Aquariums

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There are two options from Tetra: up to 4-gallon tank (27 GPH) and up to 10-gallon tank (80 GPH) filters. Item dimensions of 1 – 4-gallon filter: 3 x 3 x 7.38 inches; 5 – 10-gallon filter: 4.25 x 4 x 8 inches.


  • Easy-to-setup and maintain: Yes, this motor-submersible filter is a kind of clip-on filter, which will tank you a few minutes to set up on your tank. This filter comes with replacement cartridges. You only have to change the bio-bag filter cartridge (sold separately on Amazon) every 2 – 4 weeks depending on your stock. The filter media is also very easy to access with the hinged lid. The package comes with a complete kit for you to start your project right away: an internal filter, hinged lid, filter cartridge, tank clip, and suction cup.
  • Work well for keeping your tank clean: The filter mechanical and chemical filter cartridge includes the dual-sided mesh to catch fish waste and debris while the activated carbon removes any discolorations and unwanted odors.


  • No biological filtration stage: There is no ground for the bacteria for growing, thus, you could make up for this loss by adding a sponge filter or do water change regularly.
  • The bottom motor: You could make a DIY mesh to protect this bottom motor if it is exposed to the side that your fish could touch their fins.

Top 3: Penn-Plax Small World Aquarium Filter

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This filter is specially designed to suit small aquariums up to 5 gallons. Item dimensions: 6 x 2 x 6 inches. This filter should be connected to an Air pump and Air tubing which are sold separately on Amazon.


  • Complete 3-stage filtration system: This filter is a surprise among small compact filters designed for the small fish tank because it could provide a complete filtration system with 3 stages: mechanical, chemical, and biological. The disposable filter media cartridge contains the bio-sponge for catching debris and large particles; the carbon for removing toxic chemicals; and the zeolite for good bacteria to grow.
  • Great little and could fit all shapes:  This tiny filter could be attached to all shapes of a tank with a mounting bracket and two suction cups for strongly mounting to all types of a small tank. 


  • You need to rinse the filter cartridge to remove carbon and zeolite dust or your tank will be cloudy for days.
  • The filter kit does not come with air tubing and an adapter. However, it does come with air tube connectors. 

Top 4: Penn-Plax Cascade Hang-on Aquarium Filter

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There are two offers from Penn-Plax for the small fish tanks with this hang on back filter type: the cascade 20 (20 GPH) for up to 7-gallon tank (I will recommend you to use for up to 5-gallon tank only) and the cascade 80 (80 GPH) for up to 10-gallon tank. The overall size of Cascade 20 is 4.5” (H) x 3.75” (W) x 3” (D) and Cascade 80 is 5.75” (H) x 5” (W) x 3.4” (D).


  • Quiet: It is the quietest when running at the lowest mode, of course. When running at the highest mode, the whispering waterfall will also not annoy you.
  • Plenty of room in the filter cartridge for your creativity: The cascade 80 contains a full cartridge for a 3-stage filtration system: screen floss for mechanically screening larger particles, charcoal for chemically removing all the odors, and discolorations, and bio-sponge for growing bacteria to complete the nitrogen cycle. The cascade 20 only provides you the poly-fiber floss and charcoal but you could also add the bio-sponge for growing bacteria inside the cartridge.
  • Easy-to-clean: All parts of the cascade are easy to be disassembled for cleaning.


  • This is not suitable for a shrimp tank because of its suction power. 
  • Be careful with your water level. If you let it run dry, the motor may be overheated and ruined.

Top 5: Hygger Super Mini Aquarium Single Sponge Filter

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Many people would choose the sponge filter for a small fish tank because it is good for growing beneficial bacteria, which many other filters for the small fish tank cannot do. This Hygger Sponge filter is suitable for mini-bowls from 0.5 to 5 gallons. The filter includes two sponges, 1 suction cup, one filter body and does not include an air pump. You should buy a Hygger air pump on Amazon (ASIN: B07HKGB88M) and a 4mm air hose.


  • Great little: This mini sponge is only 3.5″ in width and 3″ in height, with the sponge circle’s diameter is 0.59’’. With this size, you will not worry about your view of your mini-bowl when placing it in or you could hide it easily in a larger tank.
  • Efficient biological filter: With the typical effects from the sponges, the good bacteria will quickly grow and clear your tank. The small and slow water currents it creates will also push more oxygen to the tank without scaring your fishes.
  • Easy-to-clean: All the parts of the filter are detachable for easy cleaning. Just remember to rinse and squeeze the sponge in the tank water instead of tap water.


  • The sponge filter creates a weak mechanical filter, thus, if you use it for a bigger tank than 5 gallons, you should use a hang-on-back filter to assist it.

Which features to consider when choosing the best filter for small fish tank?

Flow rate (GPH): The most advisable flow rate for a tank is four times of the tank size. That means if you own a 5-gallon tank, you should choose a filter with a flow rate of 20 GP. Of course, this is also dependable on what is in your tank. Each type of fish needs a different flow rate. Thus, the flow rate should also be adjustable for adapting to a broader range of stock.

Space-saving: Because your tank is small, thus, one of the first things to consider is the dimensions of the filter unit. Where should you put it or hide it in your tank? The great little filter is essential for mini tanks or bowls because it will not affect your view of the water life and give more space for your livestock.

Easy-to-setup and maintain: A small filter goes with a small tank and is not necessary to steal away too much of your time for cleaning and maintaining. A small tank is usually a choice of a starter, thus, an easy filter will be the first priority for an amateur aquarist to enjoy the hobby.

Best filter for small fish tank FAQs:

What is the good side of owning a small tank?

The most advantage that we could see clearly is everyone could own a mini tank. With a smaller amount of money and a smaller space, a mini tank is good for a dorm room, small apartment, studio room, and crowded office or classroom. 

What are the cons of owning a small tank?

Yet, the bad side of owning a small tank is that your fishes will have to live in only a few gallons of water and any small mistake could become a fatal mistake quickly. For example, overfeeding your fishes, the postponement of changing water, or even the breakdown of the filter could quickly change the water conditions and cause fish death. Thus, monitoring your water condition closely by owning a water test kit as well as carrying out exact water changes will be essential tasks of aquarists who own a mini tank. 

Which fish should I put in my small tank?

A few types of fishes could be a suitable choice for mini tanks are a single betta, Bloodfin tetra, Guppy, Platy, White cloud, and Zebra danio. Just ask the owner of the local fish store for more advice on those fishes if they are available at their store.

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