7 Fish Species that Don’t Need a Filter

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A water filter is a necessity in most scenarios since the device plays a vital role in keeping the environment balanced and fresh. The filter will play various roles, including cleaning the water of dirt and debris, diluting ammonia and other harmful chemicals, and improving oxygenation.

The problem is that the filter may be an expensive investment, and you will need to perform regular maintenance to make sure it works properly. A clogged filter will end up doing more harm than good.

Some people don’t have the time to clean and inspect the filter regularly, which brings us to today’s article. Can you have a thriving aquatic environment without having to rely on a filter? Yes, you can. There are fish species that can thrive without the need of a filter.

Today, we will discuss 7 of the most popular tank fish and why they are so beloved by aquarium keepers:

1. Betta Fish

The Betta is a gorgeous fish, capable of reaching around 3 inches in length. They have an amazing color palette with colors that will become even brighter during the mating season. A healthy Betta will live around 3 to 5 years, depending on its strain and environmental conditions.

  • BehaviorBettas tend to be friendly to other fish species, but Betta males will display aggressive behavior towards one another. They are highly territorial creatures that don’t get along with their own kind. The Betta may also attack other fish if they have larger fins. This makes Betta-only tanks more feasible than mixed ones.
  • Diet – The Betta is a born carnivore. This means you shouldn’t mix them with smaller fish since they will take them for food. Bettas need a varied diet to thrive, consisting of live food and freeze-dried meat options.
  • Tank requirements – Bettas love warmer waters with temperatures varying between 76 and 81 °F. They also need larger tanks since Betta males are territorial animals in need of a lot of water volume. This fish species will also thrive in low-oxygen waters, which is why they don’t need a filter to feel comfortable in their environment.

2. Guppies

Guppies are the most popular option among fish lovers due to their unique coloring, friendly attitude, and ease of maintenance. They come in a variety of colors, color patterns, and body shapes, making them one of the most diverse fish species around.

  • BehaviorGuppies will get along with pretty much any fish species since they are very friendly and easy-going. If anything, the guppy will often find itself at the receiving end of bullying from other fish. Males may be more jittery and energetic than the females, causing them to display slightly aggressive behavior when during territorial fights and mating competition. I recommend keeping 2-3 females for every guppy male in the tank to decrease the males’ aggression.
  • Diet – Guppies are omnivorous and will consume a variety of food options, including live and frozen food, algae, spirulina, vegetables, insect larvae, etc. You can either feed them food flakes and pellets or prepare homemade recipes containing live food and vegetables. Guppies need a diverse diet to remain healthy and happy over the years.
  • Tank requirements – Guppies need stable temperatures between 72 to 82 °F. Fluctuations are acceptable so long as they are not abrupt since sudden temperature variations will hurt your guppies. Space-wise, you should provide guppies with around 2 gallons of water per fish.

3. Gourami Fish

The Gourami species are highly popular among aquarium keepers since they are adaptable, resilient, and require minimal maintenance. Another aspect making the Gourami so popular is its diversity. Several Gourami strains are available, each with their own specifics in terms of size, tank requirements, diet, and behavior.

The most renowned ones include dwarf Gourami, honey Gourami, red Gourami, Snakeskin Gourami, etc.

  • Behavior – Males tend to be territorial towards one another but, aside from that, the Gourami fish is friendly and easy-going. It makes for a great choice for community tanks, so long as you pair them with non-aggressive tank mates.
  • Diet – Gouramis are omnivorous and will eat a variety of foods, just like guppies. You should provide them with a balanced diet, consisting of live and frozen meat-based foods, along with veggies like peas, spinach, lettuce, carrots, cucumber, zucchini, etc. The Gourami may require fresh and live food during the breeding period.
  • Tank Requirements – The tank’s temperature should range between 76 to 82 °F since Gouramis enjoy warmer waters. They also enjoy environments heavy in vegetation since it will mimic their natural habitat. This provides the Gouramis with hiding spots and plenty of opportunities for exploration.

4. Corydoras

The Corydoras genus encompasses over 160 species, ranging in size between 1.2 to 2.5 inches, which is pretty much in the guppies’ ballpark. They are easy to maintain and can thrive in community tanks, so long as you don’t pair them with large or overly aggressive species.

  • Behavior – The Corydoras are friendly and more introverted than other fish species. They like to spend much of their lives in deeper waters, looking for food and hiding near the substrate. The Corydoras will go at the water’s surface occasionally to take a few gulps of oxygen and return to their comfort zone immediately after.
  • Diet – Corydoras are omnivores and require a varied diet to remain healthy. The good thing is that this fish will eat almost anything that can fit in their tiny mouths. Even more important is the fact that they are a bottom-dwelling species, making them ideal tank mates with top dwelling fish. This way, the Corydoras will clean all the food residues sinking in to the substrate. Setting that aside, you should feed your Corydoras directly and not rely on them surviving on other fish’s crumbles. Corydoras will thrive on shrimp pellets, algae rounds, and bottom-feeding-specific tablets.
  • Tank Requirements – The ideal temperature for Corydoras revolves around 72 to 79 °F, which is very similar to that of guppies. They don’t need a specific tank size, since they aren’t that territorial by nature. They will simply adapt to what you have, so long as the tank is not overcrowded.

5. Zebra Danios

The Zebra Danios is another small and friendly that can adapt to both fast-moving streams and stagnant waters. You can identify the species thanks to its horizontal blue and purple/reddish stripes and its surplus of energy. The Zebra Danios fish are very active swimmers that will adapt to pretty much any environment.

  • Behavior – Peaceful, vibrant, and playful. Zebra Danios are schooling fish that thrive in groups of at least 5 individuals. They should also have enough room to explore since Zebra Danios are inquisitive by nature.
  • Diet – Anything that goes for guppies goes for Zebra Danios. The latter are omnivores and will eat pretty much anything so long as it’s edible. Make sure you provide your Zebra Danios with a balanced diet, mixing live food with vegetables for optimal nutrient intake.
  • Tank Requirements – Zebra Danios prefer colder waters with temperatures varying between 64 to 74 °F. This makes them incompatible with species like guppies, which prefer warmer environments.

6. Neon Tetras

Neon Tetras are small, colorful, and joyful and will enrich you with their presence for up to 5 years or more, given optimal environmental conditions. This tiny spark of color will grow up to 1.5 inches with a torpedo-shaped body and vivid colors that will vary in intensity. The Neon Tetra will dull its colors when resting, becoming alarmed of threaten, or when sick.

  • BehaviorPeaceful with strong social predilections. The Neon Tetra is a schooling species that prefers the company of its own kind. You should keep it in a group of at least 15 fish to provide them with peace of mind and comfort. Otherwise, they might become stressed and feel threatened.
  • Diet – Neon Tetras are omnivorous. Feed them a balanced diet of animal-sourced protein and plants and vegetables and they will remain healthy and active long-term.
  • Tank Requirements – You should have at least 10 gallons of water for a Neon Tetra group. However, I would suggest a larger tank thanks to this species’ curious nature.

7. Japanese Rice Fish

The Japanese Rice Fish (Japanese Killifish or Medaka) is a popular fish species for aquarium use. They are small, golden, with often blue eyes, and, most importantly, glow in the dark.

  • Behavior – This species is peaceful and friendly, especially since it has no other option. The Japanese Rice Fish is small and relies on schooling behavior to remain safe from predators. Don’t pair them with overtly large fish, or they might turn into food for the more voracious tank inhabitants.
  • Diet – Omnivorous. The Japanese Rice Fish requires a balanced diet consisting of plants, vegetables, and animal-sourced food. You can either buy their food from fish shops, have cultures of live food at home, or prepare their meals yourself. I’ve written detailed articles on fish food options and included homemade recipes to help you out.
  • Tank Requirements – Fortunately, the Japanese Rice Fish doesn’t require large spaces. A 10-gallon tank should suffice for a group of 6 fish. Just make sure you add plenty of vegetation to keep them satisfied and comfortable in their environment. The ideal temperature ranges between 64 and 72 °F, which already makes them incompatible with several fish species, including guppies.

Can Fish Survive Without a Filter?

Yes, they can. As a minus,  you need to rely on water changes to keep them healthy. The real problem here is that the filter will also improve the water’s oxygenation level, aside from cleaning the water and removing ammonia. Without that, your fish will suffocate and die.

The good news is that the tank filter isn’t absolutely necessary. You can oxygenate the fish’s environment via regular water changes. If you don’t have a filter, you will probably need to change around 15% of the tank’s water every 4-5 days. The frequency will also depend on the tank’s size and how many fish it houses.

How to Care for Fish With no Filter?

Most people use filters because it stabilizes the fish’s environment, requiring less intervention on their part. But if you don’t want to use a filter, you need to learn how to stabilize the aquatic habitat. This means resorting to solutions like:

– Getting a Bigger Tank

The bigger the tank, the higher the water volume, and the more oxygen will be available. I suggest getting a tank bigger than what your fish need. It’s no point in getting a 50-gallon tank if you’re overcrowding it anyway.

The tank’s size depends on the fish species you have. To give you an example, one guppy requires 2 gallons of water. So, in theory, you can house 25 guppies in a 50-gallon tank. If you have no filter, you should only keep 15 or 20 at most. This will provide the fish with more available oxygen and decrease the frequency of the water changes.

– Use Live Plants

Having live plants in the aquarium is a great way of oxygenating the water naturally. Plants will use photosynthesis to consume carbon dioxide, produce oxygen during the daytime, and reverse the process during nighttime.

This shouldn’t be a problem since guppies only need low levels of lighting for 8 hours during nighttime. Otherwise, you will keep the lights on, which means that the plants will produce oxygen for at least 16 hours per day.

Naturally, you still need to perform regular water changes to clear ammonia and other harmful compounds.

– Establish the Tank

The tank is established when the biological filtration system has matured. We’re talking about the cultures of live, beneficial bacteria that consume ammonia and nitrites, and improve water oxygenation. These cultures require time to settle, generally between 6 to 8 weeks.

This is why it’s important to perform the nitrogen cycle before adding the fish to their new environment. It’s then even more important to avoid disturbing the tank’s biofilm. This is why you only need to change around 10-15% of the water each time. Anything more than that can disrupt or even kill the cultures of beneficial bacteria inhabiting the aquarium.

– Use a Thick Substrate

The substrate’s thickness is also essential to provide plants with a solid base. How thick the substrate should be depends on the plants and the substrate’s type. Some plants have longer roots and require a thicker substrate than others.

For instance, if you’re using sand, the substrate can go to 1 to 1.5 inches in depth. Gravel can get deeper than that, at around 2-3 inches. However, don’t go overboard with it since excessively thick substrate will block or even crush the plants’ roots.

The substrate’s type also varies depending on your goals. Sand substrate will keep the fish waste and food residues at the surface, allowing you to clean them easier. On the other hand, gravel consists of larger granules, allowing residues to fall through. You will need to vacuum it regularly to make sure you get them out.

– Regular Water Changes

Water changes are the bedrock of any stable and thriving aquatic environment. You need to perform weekly water changes to keep the oxygen levels within the ideal parameters and benefit the aquatic fauna, both macro, and micro.


There are species of fish that don’t require any tank filter. Today’s article has presented you with 7 of the most popular ones, but you can find more.

Just know that not using a filter requires additional efforts on your part and careful considerations when preparing your fish’s environment.

Author Image Fabian
I’m Fabian, aquarium fish breeder and founder of this website. I’ve been keeping fish, since I was a kid. On this blog, I share a lot of information about the aquarium hobby and various fish species that I like. Please leave a comment if you have any question.
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