What Fish Don’t Need A Filter (And Why): 10 Fish Species

An Aquarium With Different Fish Species
An Aquarium With Different Fish Species
Dr. Mollie Newton
Published by Dr. Mollie Newton PHD| Senior Editor
Last updated: May 24, 2024
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In a Nutshell

Want an easy fish tank? Betta Fish, Dwarf Pufferfish, Ember Tetras, Guppies, and others can live happily without a filter. They are special fish that don’t need much to stay healthy and make your aquarium look great.

Some fish species have adapted to flourish in aquariums without the need for a filter, making them perfect for those looking for simple aquarium care. These extraordinary species have unique traits that allow them to thrive in low-maintenance settings. Knowing which fish species don’t require filters helps aquarium enthusiasts create the best environment for these captivating marine creatures. This article will delve into a diverse array of attractive fish species that bring both beauty and ease to your aquarium.

Article Summary

  • Some fish species have evolved to thrive in aquariums without the need for a filter, making aquarium care simpler.
  • These fish possess unique adaptations that allow them to live in low-maintenance environments.
  • To enhance the environment for filterless aquariums, use the right substrate and incorporate live plants for natural filtration.

Nature’s Filtration: The Power of Aquarium Plants

In our journey through the enchanting world of filter-free aquariums, the significance of live plants cannot be overstated. These verdant wonders are more than just decorative elements; they are the heart of a natural filtration system.

Plants are adept at absorbing excess nutrients and detritus, thereby reducing the need for mechanical filtration. Their presence creates a harmonious balance in the ecosystem, ensuring cleaner water and a healthier environment for your aquatic friends.

Incorporating a variety of plants not only enhances the aesthetic appeal of your tank but also promotes a diverse and balanced ecosystem. Choose species that are known for their filtration capabilities, such as Hornwort or Java Fern, to create a lush, self-sustaining underwater garden.

This approach not only adds visual depth to your aquarium but also provides a haven for your fish to explore and thrive.

Betta Fish

Blue Betta at the Bottom of an Aquarium
Blue Betta at the Bottom of an Aquarium

Scientific Name: Betta splendens

Also Known as: Siamese fighting fish

Lifespan: These beautiful fish can live for an average of 2 to 4 years in captivity. However, with proper care and a healthy environment, some bettas have been known to live up to 5 years or even longer.

Appearance and Size

Betta fish are renowned for their vibrant colors and flowing fins. They come in various shades, such as red, blue, purple, and even multicolored combinations. The males are especially striking with their long, flowing fins that resemble elegant robes. On the other hand, females have shorter fins and are less flamboyant in appearance. In terms of size, bettas typically grow to about 2.5 to 3 inches long.

Betta Fish Diet

In the wild, bettas feed on small insects and larvae. As aquarium fish, they require a well-balanced diet consisting of both dry and live foods. High-quality betta pellets or flakes should be the mainstay of their diet. You can supplement their meals with frozen or live foods like bloodworms or brine shrimp. It’s important not to overfeed them as it can lead to obesity and health issues.

Temperament and Compatible Tank Mates

Bettas are known for their feisty nature, which is why they were historically used for fighting matches (hence the name “Siamese fighting fish”). However, it’s crucial to note that keeping them in small containers or bowls is not ideal as it restricts their movement and may lead to stress-related illnesses.

Bettas are generally solitary fish but can coexist peacefully with certain tank mates. Snails like nerite snails or mystery snails can be suitable companions as they help clean the tank and provide an interesting dynamic. Additionally, small, non-aggressive bottom-dwelling fish like Corydoras catfish or small loaches can also be compatible with bettas.

Why Betta Fish Don’t Need a Filter

Betta fish are unique because they possess a specialized labyrinth organ that allows them to breathe oxygen directly from the air above the water’s surface. This organ enables them to extract oxygen from low oxygen levels in the water, making them less dependent on filtration systems that primarily serve to aerate the water for other fish species.

Dwarf Pufferfish

Dwarf Puffer Fish
A Dwarf Puffer Fish Exploring The Tank

Scientific Name: Carinotetraodon travancoricus

Also Known as: Malabar pufferfish, pygmy pufferfish, or pea pufferfish

Lifespan: Dwarf Pufferfish have a relatively short lifespan, typically living for about 3 to 5 years.

Appearance and Size

Dwarf Pufferfish are small in size, reaching an average length of only 1 to 2 inches. They have a round body shape with distinct markings. Their coloration can vary from greenish-brown to yellow or even orange.

Dwarf Pufferfish Diet

These little pufferfish are carnivores and have a unique feeding habit. They primarily feed on snails, especially pond snails. The Dwarf Pufferfish has strong jaws that allow it to crush the shells of its prey easily.

Temperament and Compatible Tank Mates

Dwarf Pufferfish are known for their feisty temperament. They can be quite aggressive towards other fish, especially if they feel threatened or if their territory is invaded. Due to their territorial nature, it is best to keep them in a species-only tank or with other non-aggressive fish that can hold their own.

Why Dwarf Pufferfish Don’t Need a Filter

One fascinating aspect of Dwarf Pufferfish is their ability to survive without a traditional filter in their tank. These fish possess a unique adaptation called a labyrinth organ, which allows them to breathe atmospheric air directly from the water’s surface.

Another reason why Dwarf Pufferfish don’t need a filter is due to their diet preference for snails. Snails produce waste that contributes to the nitrogen cycle in the aquarium, which helps to maintain water quality by breaking down harmful substances. The pufferfish’s diet of snails naturally helps keep the tank clean and reduces the need for additional filtration.

Ember Tetra Fish

Ember Tetra
The Brightly Colored Ember Tetra

Scientific Name: Hyphessobrycon amandae

Lifespan: Ember Tetra Fish is relatively short-lived compared to other species, living up to 2 years.

Appearance and Size

Measuring only about 0.8 inches (2 centimeters) in size, these tiny fish can easily be overlooked due to their small stature. But don’t let their size fool you – they possess stunning colors that range from fiery red-orange to bright yellow.

Ember Tetra Diet

Ember Tetras are not picky eaters. They will happily consume a variety of foods, including flakes, pellets, and live or frozen foods such as brine shrimp or daphnia. Providing them with a balanced diet ensures their overall health and vitality.

Temperament and Compatible Tank Mates

In terms of temperament, Ember Tetras are peaceful fish and social creatures that thrive in groups of at least six individuals. They enjoy swimming together in schools and feel more secure when surrounded by their own kind.

When selecting tank mates for your Ember Tetras, it’s important to choose species that share similar water requirements and temperaments. Good companions include other small peaceful community fish like neon tetras or guppies.

Why Ember Tetra Don’t Need a Filter

One fascinating aspect of Ember Tetra Fish is that they don’t require a filter in their tank setup. While most aquariums rely on filters to maintain water quality by removing waste and toxins, these hardy little fish can adapt well even without one.

Guppy Fish

fish guppy pet isolated on black background
A Colorful Male Guppy

Scientific Name: Poecilia reticulata

Also Known as: Millionfish, Rainbow fish

Lifespan: Guppies have a lifespan of around 2 to 3 years, making them a great choice for beginner fish keepers looking for low-maintenance pets.

Appearance and Size

Guppies are known for their striking appearance. The males typically have colorful bodies with long flowing tails, while the females tend to be more plain-looking. Their size ranges from about 1 to 2 inches in length, making them perfect for smaller tanks or community setups.

Guppy Diet

Guppies are omnivores and have a varied diet. They will happily consume both dry and live foods. A balanced diet for guppies includes high-quality flakes or pellets specifically formulated for small tropical fish. You can also supplement their diet with live or frozen foods such as brine shrimp, daphnia, or bloodworms.

Temperament and Compatible Tank Mates

Guppies are generally peaceful and social fish that can coexist well with other small freshwater fish species. However, it’s important to consider the temperament of potential tank mates when choosing companions for your guppies. Avoid aggressive or fin-nipping species that may harm the guppies’ delicate fins.

Some suitable tank mates for guppies include: Neon tetras, Corydoras catfish, Platies, Swordtails, and Endler’s livebearers.

Why Guppy Fish Don’t Need a Filter

Guppy fish are hardy and adaptable, which allows them to thrive without a filter. They can tolerate varying water conditions and fluctuating temperatures. Additionally, guppies have a high metabolism, producing less waste compared to larger fish.

Japanese Rice Fish

Japanese rice fish is scientifically known as Oryzias latipes
The Tiny Japanese Rice Fish

Scientific Name: Oryzias latipes

Also known as: Medaka

Lifespan: Japanese Rice Fish have an average lifespan of 2 to 3 years when kept in suitable conditions. However, with proper care and a well-maintained environment, they can live up to 5 years.

Appearance and Size

These small fish have a slender body shape and typically grow to about 1-2 inches in length. They come in various colors such as silver, gold, orange, or even transparent. Their long fins give them an elegant appearance.

Japanese Rice Fish Diet

Japanese Rice Fish are omnivorous creatures, meaning they eat both plants and small organisms. In their natural habitat of rice paddies, they feed on insects, algae, small crustaceans, and organic matter present in the water. In captivity, they can be fed a diet consisting of high-quality flakes or pellets supplemented with live or frozen foods like brine shrimp or daphnia.

Temperament and Compatible Tank Mates

These fish have a peaceful temperament which makes them ideal for community tanks. They get along well with other non-aggressive species, such as guppies, tetras, danios, and rasboras. It’s important to avoid keeping them with larger or aggressive fish that may bully or prey upon them.

Why Japanese Rice Fish Don’t Need a Filter

One remarkable feature of Japanese Rice Fish is their ability to tolerate low oxygen levels thanks to their adaptation to oxygen-poor environments like rice paddies. This unique characteristic allows them to thrive without the need for a filter in their tank. The rice paddies they inhabit naturally have stagnant water, and the fish have evolved to extract oxygen from the air above the water’s surface.

Thermal Harmony: The Interplay of Water Temperature and Oxygen

Understanding the interplay between water temperature and oxygen levels is crucial in the realm of unfiltered aquariums. The right temperature is essential for maintaining a stable and oxygen-rich environment, especially for species like the charming Goldfish.

Cooler waters hold more oxygen, making them ideal for such species. This balance is key to ensuring the well-being and vitality of your aquatic inhabitants.

To maintain this delicate equilibrium, it’s important to monitor the temperature regularly and make adjustments as needed. This can be achieved through strategic placement of your aquarium away from direct sunlight and using aquarium heaters designed for small tanks.

By keeping a vigilant eye on the thermal conditions of your tank, you ensure a serene and thriving habitat for your fish.

Paradise Fish

Paradise Fish Swimming in Aquarium
Paradise Fish Swimming in an Aquarium

Scientific Name: Macropodus opercularis

Also Known as: Blue paradise fish, blue paradise gourami, or paradise gourami

Lifespan: up to 10 years

Appearance and Size

Paradise Fish are visually stunning creatures. They boast vibrant hues of red, blue, orange, and green that shimmer in the light. Growing up to 4 inches in length, these small-sized fish make quite an impact with their striking appearance.

Paradise Fish Diet

These fish species are not picky eaters. They have an omnivorous diet, which means they consume both plant matter and small insects. Commercially available fish flakes or pellets serve as a good staple diet for them. Supplementing their meals with live or frozen foods like brine shrimp or bloodworms provides essential nutrients and keeps them healthy.

Temperament and Compatible Tank Mates

Known for their peaceful nature, Paradise Fish can be kept with other non-aggressive species without any issues. However, it’s important to remember that male Paradise Fish can display territorial behavior towards each other. Therefore, it’s advisable to keep only one male per tank unless you have a large enough aquarium where territories can be established easily.

Here are some compatible tank mates for Paradise Fish: Guppies, Tetras, Corydoras Catfish, and Cherry Barbs. And avoid keeping them with fin nippers or aggressive species that may harm the delicate fins of the Paradise Fish.

Why Paradise Fish don’t need a filter

One unique aspect of the Paradise Fish is its ability to thrive without the need for a filter in its tank. While most fish require filtration systems to maintain water quality by removing waste and toxins, this hardy species has adapted well to varying water conditions.

The reason behind this lies in their natural habitat. In the wild, Paradise Fish inhabit slow-moving waters with low oxygen levels. Over time, they have developed a labyrinth organ that allows them to breathe air directly from the surface. This adaptation enables them to survive in environments with less oxygen and makes them less dependent on filtration systems.

Pygmy Corydoras

Also known as Corydoras pygmaeus
A Pygmy Cory Resting on Driftwood

Scientific Name: Corydoras pygmaeus

Lifespan: up to 5 years

Appearance and Size

Pygmy Corydoras are small in size, typically reaching about 1 inch (2.5 centimeters) when fully grown. They have a sleek body shape with a silver or bronze coloration. Their eyes are large and expressive, adding to their adorable appeal.

Pygmy Corydoras Diet

These fish species are not picky eaters! They enjoy a varied diet consisting of both dry and live foods. Sinking pellets or flakes specifically designed for bottom-dwelling fish make an excellent staple diet for them. They relish the occasional treat of live or frozen foods like brine shrimp or bloodworms.

Temperament and Compatible Tank Mates

Pygmy Corydoras have a peaceful temperament, making them ideal community fish. They thrive in groups of at least six individuals since they are social creatures by nature. Keeping them in larger numbers helps alleviate stress and promotes their natural behavior.

These little corys get along well with other peaceful species that share similar water requirements. Some suitable tank mates include small tetras, rasboras, guppies, and dwarf shrimp such as cherry shrimp or amano shrimp.

Why Pygmy Corydoras Don’t Need a Filter

Pygmy Corydoras can thrive without a filter due to their small size and low bioload. They produce minimal waste and contribute to the beneficial bacteria in the aquarium. Regular water changes can replace the function of a filter.

Sparkling Gourami Fish

Sparkling Gourami by BEDO
Sparkling Gourami Exploring The Tank

Scientific Name: Trichopsis pumila

Also Known as: Dwarf Croaking Gourami, Green Croaking Gouriem, Purring Goumi, and Pygmy Gourami

Lifespan: These small and vibrant fish have a lifespan of around 3 to 4 years, making them a delightful addition to any aquarium.

Appearance and Size

Sparkling Gouramis are known for their stunning appearance. They have a slender body with bright colors that shimmer under the light. The males display more intense colors, featuring shades of blue, green, and red on their bodies. On the other hand, females have more subdued hues.

In terms of size, these gouramis are relatively small compared to other species in the family. They typically grow up to 1.5 inches (3-4 cm) in length, making them suitable for smaller tanks or community setups.

Sparkling Gourami Diet

They are not picky eaters. These omnivorous fish will happily consume both dry and live foods. A well-balanced diet includes high-quality flakes or pellets supplemented with occasional treats like brine shrimp or bloodworms.

Temperament and Compatible Tank Mates

Sparkling Gouramis are generally peaceful and non-aggressive creatures that can thrive in community tanks. However, due to their small size and delicate nature, it’s crucial to choose tank mates carefully.

These are some compatible tank mates for Sparkling Gouramis. Small tetras, like Neon Tetras or Ember Tetras; Peaceful rasboras, such as Harlequin Rasboras; Dwarf shrimp, like Cherry Shrimp or Amano Shrimp; Snails, like Nerite Snails or Mystery Snails.

Why Sparkling Gourami Don’t Need a Filter

Sparkling Gouramis can thrive without a traditional filter system because they naturally adapt to slow-moving and stagnant waters. They have low waste production, which means they don’t require a filter to maintain water quality.

White Cloud Mountain Minnows

A White Cloud Mountain Minnow Sifting The Tank Bottom
A White Cloud Mountain Minnow Sifting The Tank Bottom

Scientific Name: Tanichthys albonubes

Lifespan: These tiny fish have an average lifespan of 3-5 years.

Appearance and Size

White Cloud Mountain Minnows are quite eye-catching. This cold water fish have a slender body with a silver coloration and a prominent dark stripe running horizontally along their sides. They possess vibrant red fins that add a pop of color to their overall look. And they and can grow up to 1.5 inches in size that makes this fish survive in a fish bowl.

White Cloud Mountain Minnow Diet

In terms of diet, these minnows are not picky eaters. They will happily consume a variety of foods, including flakes, pellets, live or frozen brine shrimp, and daphnia. It’s important to provide them with a balanced diet to ensure their health and vitality.

Temperament and Compatible Tank Mates

One notable characteristic of White Cloud Mountain Minnows is their peaceful temperament. They are known for being friendly and sociable towards other fish species in the tank. This makes them suitable tank mates for other peaceful community fish like tetras, danios, and guppies.

Why don’t White Cloud Mountain Minnows need a filter?

These minnows can thrive in tanks without filters due to their unique adaptation to low-oxygen environments. In the wild, they inhabit mountain streams where water flow is minimal and oxygen levels may be lower compared to larger bodies of water. These resilient fish have evolved the ability to extract oxygen from both the water column and atmospheric air through specialized structures called labyrinth organs. This adaptation allows them to survive in conditions with lower oxygen content.

Zebra Danios

Zebra Danio
The Stunning Zebra Danio

Scientific Name: Danio rerio

Also Known as: Zebrafish

Lifespan: Zebra Danios have a relatively long lifespan for a small fish, typically living for about 3-5 years when kept in optimal conditions.

Appearance and Size

These feisty fish are easily recognized by their striking black and white stripes that resemble the patterns of a zebra, hence their name. They have slender bodies that grow to an average length of around 1-2 inches (2.5-5 cm). Despite their small size, they can bring a burst of energy to any aquarium.

Zebra Danio Diet

They are not picky eaters. In the wild, they primarily feed on small insects and larvae found in rivers. In captivity, they readily accept various types of food such as flakes, pellets, freeze-dried or frozen foods like bloodworms or brine shrimp. It’s essential to provide them with a balanced diet to ensure their overall health and vitality.

Temperament and Compatible Tank Mates

Zebra Danios are known for their active and playful nature. They are social fish that thrive in groups of at least six individuals or more. Keeping them in larger numbers helps reduce aggression within the group.

Zebra Danios generally get along well with other peaceful community fish species like tetras, rasboras, guppies, and corydoras catfish. However, it’s important to avoid keeping them with aggressive or fin-nipping species that may stress or harm them.

Why Zebra Danios Don’t Need a Filter

Zebra Danios are known for their ability to thrive in various aquarium setups, including those without a filter. They are incredibly hardy fish that can adapt to different water conditions, allowing them to tolerate lower water flow and do well in tanks with minimal filtration.

Enhancing the Environment: Substrate and Live Plants

beautiful fishes swimming in a planted tropical freshwater aquarium
A Planted Tank With Different Fish Species

Creating a thriving habitat for fish that don’t need filters involves more than just providing clean water. The right substrate and live plants play a crucial role in enhancing the overall environment of the aquarium.

Choosing the Right Substrate

Choosing the right substrate is essential for creating a natural environment for fish that don’t need filters. Gravel provides a stable base for plants to grow, while sand offers a soft substrate preferred by some fish species. The right substrate not only enhances the aesthetics but also provides hiding places for the fish.

Live Plants for Additional Filtration

Incorporating live plants into your filterless setup offers numerous benefits. These plants act as natural filtration systems by absorbing excess nutrients, preventing algae growth and keeping your tank clean. Plants also produce oxygen through photosynthesis, increasing oxygen levels in the aquarium. Additionally, a well-planted tank promotes beneficial bacteria growth, ensuring optimal water quality by breaking down waste products.

Oxygenation Elegance: Maximizing Surface Area in Your Aquatic Eden

The art of crafting a filter-free aquarium involves a keen focus on maximizing the water’s surface area. This is crucial for facilitating effective oxygen exchange, a process vital for the health and well-being of your aquatic inhabitants.

A larger surface area allows for more oxygen to dissolve into the water and for carbon dioxide to escape, creating an optimal breathing environment for your fish.

To enhance this aspect of your tank, consider designing your aquarium with ample open water surface. Avoid overcrowding the surface with floating plants or decorations, ensuring that there is plenty of room for air-water interaction.

This design consideration not only promotes the health of your fish but also adds a touch of elegance and openness to your aquatic setup, making it a true centerpiece of your home.

Researching Plant Species Compatibility

Before adding live plants to your tank, it’s important to research their compatibility with your fish species. Some fish may eat or uproot certain plants, so choose species that can coexist harmoniously. Consider factors like lighting, temperature, and pH levels when selecting plants. Thorough research will help you create a filterless aquarium that benefits both your fish and provides a natural-looking environment.

Frequently Asked Questions

What kind of fish can live without a filter?

Fish that can live without a filter are typically hardy, low-maintenance species that can tolerate varying water conditions. Some examples include Betta fish, Guppies, and White Cloud Mountain Minnows. These fish can survive in tanks without a filter, but proper care and regular water changes are essential to maintain a healthy environment for them.

Can I keep fish without a filter?

Yes, you can keep fish without a filter, but it requires careful attention to water quality and maintenance. For smaller tanks or certain hardy fish, it’s possible to maintain adequate water conditions through regular water changes and proper feeding. However, a filter is recommended for most aquarium setups as it helps maintain stable water parameters and reduces the risk of harmful ammonia and nitrite buildup. If you choose to keep fish without a filter, be prepared to invest more time in tank maintenance to ensure the well-being of your fish.

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