Fish that don’t need a filter? All fish need a filter. There’s no substitute for it. Frankly, I faced a moral dilemma when I was approached to write this article. My first reaction was, “No. It’s unethical to create content on a topic like this.”
But once I recollected myself, I realized that a filter may not be available to everyone at all times. Sometimes, it can break or go out of function. Other times, there can be a power outage.
Yes, there are fish you can keep without a filter but ONLY FOR A SHORT TIME. Not all fish are made the same. Some are naturally more hardy than others.
Therefore, if you get a few things right, such as performing adequate water changes, strategically placing plants, and so on and so forth, certain fish species can live without a filter for a certain duration.
Some of them are:
- Bettas (Betta splendens)
- Zebra Danios (Danio rerio)
- Guppies (Poecilia reticulata)
- Ember Tetras (Hyphessobrycon amandae)
- White Cloud Minnows (Tanichthys albonubes)
- Sparkling Gouramis (Trichopsis pumila)
- Pygmy Corydoras (Corydoras pygmaeus)
- Dwarf Puffer Fish (Carinotetraodon travancoricus)
- Scarlet Badis (Dario dario)
- Six-Ray Corydoras (Aspidoras pauciradiatus)
- Endler’s Livebearers (Poecilia wingei)
The fish species I listed above are among the hardiest fish we know in the hobby. They’re pretty tolerant and forgiving of beginner’s mistakes, such as taking too long to install a filter.
Anyhoo, when choosing fish that can go without a filter for a bit longer, don’t forget to consider the following points.
Choose Hardy Fish
This is self-explanatory. Tanks without filters are naturally more inclined to get polluted quickly. The toxic buildup of harmful compounds like ammonia and nitrite will happen more often and more frequently.
Therefore, you must choose fish that are ‘built strong’ – genetically sound fish. For instance, if you choose fancy goldfish or jellybean cichlids, these fish would naturally suffer more in a filterless tank due to their genetic defects.
Choose Small Fish
Small fish means small bioload. And small bioload means less pollution. If you were to keep goldfish in a filterless tank, I’d say it’d be a foolproof way to kill the fish. Goldfish are turtles of the fish world. Yes, they poop a lot.
Small fish naturally have a small appetite and therefore excrete small amounts of waste. This way, the water parameters will remain relatively safe for more extended periods.
Choose Solitary Fish
Once again, more fish means more bioload. If there are multiple fish in the tank, there will be more collective waste. There will be more leftover food and poop – leaving your tank prone to sudden spikes of ammonia.
If the ammonia levels rise, the fish will suffocate, and its bodily functions will fail. Some common signs of ammonia poisoning in fish are reddened gills, labored breathing, lethargy, and loss of appetite.
Hence, choosing fish that love to live alone is super important. If you keep schooling fish like barbs alone in a filterless tank, they will become super anxious and stressed – causing their health to fail.
Choose Coldwater Fish
I know some fish I mentioned in the list above are not coldwater fish. However, there’s a reason I included this pointer. Lack of filtration means more frequent water changes. And more frequent water changes mean sudden fluctuations in temperature.
Coldwater fish are naturally more adept at handling changes in temperature than tropical and saltwater fish.
That being said, I sincerely hope that you aren’t keeping fish without both a filter and heater!
Before we discuss the general needs and characteristics of the fish listed above, let’s find out why filters are essential – in fact, indispensable – for your fish.
Why Do Fish Need Filters?
Filters are important for fish for the same reasons good air is important for us. A filter will eliminate the debris, nullify the toxic buildup of ammonia and nitrates, and oxygenate the water. So unless you want your fish to drop like flies sooner or later, it’s absolutely essential to install a filter.
It Breaks Down Ammonia
Ammonia is downright lethal for fish, no matter how hardy your fish is. Ammonia is formed in a closed system like a fish tank when uneaten food and other organic matters decompose.
The buildup of this harmful compound is known to suffocate fish, burn their skin, and cause gill and internal organ damage.
Therefore it’s super essential to get a filtration system to break down ammonia into less harmful compounds.
Adding live plants to the aquarium will help as they consume ammonia. But the plants will only consume the amount they actually need, right?
If you have a heavily planted tank with just a few fish, maybe your fish will be spared ammonia poisoning. But this is still a highly unlikely scenario.
A filter contains biological media where the good bacteria colonies reside and thrive. And these tiny organisms work collectively to transform harmful ammonia into less toxic compounds.
It Gets Rid Of Algae
The water in your fish tank has to be circulated perpetually. If the water becomes stagnant, it becomes a breeding ground for algae.
If there’s no filtration system, there will be no water flow. As a result, algae will grow prolifically. In addition to being unsightly, algae in an aquarium are also the telltale sign of imbalance in the tank and high levels of pollutants.
And it can have numerous consequences. For example, it will steal nutrition from your plants, raise the tank’s pH suddenly, starve the tank of oxygen at night and trap the fish.
It Supports Plants Growth
You already know that plants need several micro and macronutrients to ensure proper growth. And the primary source of these indispensable nutrients in an aquarium is the water column.
And if you don’t have a proper filtration mechanism in place, the water will not be circulated throughout the tank. And when water isn’t circulated, the plants will not receive the necessary nutrients.
To make the matter worse, your plants will have to directly compete with prolifically growing algae for whatever little nutrition the tank has to offer.
Therefore, we can conclude that filters aren’t just crucial for fish and are equally critical for plants.
It Doesn’t Stress The Fish
It’s obvious that if you don’t have a filter in your tank, you will be performing more frequent water changes and deep-cleaning the tank numerous times a month.
Being netted, getting transferred, then coming back home to completely different water parameters will undoubtedly shake your poor fish to the core.
That’s because no matter how hardy the fish is, not a single one of them likes sudden or frequent shifts in their environment or parameters.
And when stressed, a fish’s body inhibits the production of white blood cells – lowering its immunity and exposing it to numerous pathogens.
So, a sound filtration system is vital in the sense that you don’t have to handle the fish as much as you’d have to in a filterless environment. So naturally, the fish will be less stressed and happier.
Maintenance Will Be Easy
Filtration systems are a far cry from being maintenance-free. For instance, if you allow the debris to be collected in the mechanical filter, it will decompose into ammonia – negating its primary purpose.
However, a filter will also save you a lot of time and elbow grease. It will ensure that you don’t constantly have to be on your toes to maintain the water parameters.
The frequency of performing water changes and performing water tests will reduce drastically – sparing you a reasonable amount of time and effort in both the long run and short run.
A Breakdown Of A Filter’s Functions
Filters these days come equipped with all 3 kinds of filtration systems: biological, chemical, and mechanical.
Biological filters decompose the poisonous ammonia buildup from leftover food and fish waste. Therefore, all tanks absolutely need biological filtration, which is, in fact, the cheapest and most efficient way to break down toxic ammonia.
Mechanical filtration traps small waste particles like plant leaves and leftover food, allowing them to be removed from the tank before they decompose and produce ammonia.
Chemical filtrations like zeolite and activated carbon work to remove harmful substances like heavy metals and dissolved organics through chemistry (for example, “ion-exchange resins” or “adsorption.”
Chemical filtrations work the best to tackle short-term problems like removing medications and chemicals after they’ve served the purpose or purifying tap water.
Thanks to science, filters these days come fully equipped with all 3 kinds of filtration systems to keep your tank’s water parameters to the T.
Our Filter Recommendation
We use the Marineland Penguin Bio-Wheel Power Filter at Urban Fishkeeping for most of our fish tanks.
I remember choosing this product after going through dozens and dozens of reviews on Amazon.
Have a look at some bells and whistles of this aquarium filter:
- Multistage filtration system delivers chemical, biological, and mechanical filtration.
- Patented Bio-Wheel technology offers wet/dry biological filtrations
- Available in 5 sizes suitable for all aquariums
- Effectively removes waste, odors, and discoloration
Now let’s have a deeper look into these hardy fish that can go on without a filter for a while.
Bettas (Betta splendens)
|76-81 degrees F
A fish as stunning as a betta, you’d think they are extremely delicate. But the opposite is true. Famous for their iconic tails and brilliant colors, bettas are among the hardiest fish available in the hobby.
Also, bettas are carnivores. They love a meaty diet. So you can give them protein-rich pellets, as well as freeze-dried and live food. In their natural habitat, bettas would primarily snack on insects and larvae.
Bettas are named Siamese Fighting Fish, and they’re very true to their name. These are aggressive fish – especially males, who fight even their own reflection.
A sorority of female bettas is very much possible. But keeping two males in the same tank is a big no-no, no matter how big the tank is.
While bettas would love to lead solitary lives, ghost shrimps, mystery snails, catfish, and loaches would make excellent tankmates.
Zebra Danios (Danio rerio)
|Up To 5 Years
|64-74 degrees F
Zebra danios, native to South Asia, are famous for the iconic purple stripes that run along their body. What impresses me the most about these fish is their ability to withstand currents of fast-moving streams but also thrive in stagnant waters.
Zebra danios are omnivores. Thus, they’re pretty easy to feed. You can give them pellets, flakes, blanched veggies, and occasionally, live and frozen invertebrates.
Zebra danios are social and peaceful for the most part. As schooling fish, they love to live in big groups. Therefore, you should aim to keep at least 6 of them together.
If kept alone or in smaller numbers, zebra danios tend to get severely stressed. They will then resort to nipping fins.
Fish like loaches, corys, barbs, swordtails, and gouramis would make ideal inhabitants for a danios tank. But since they’re known to nip fins, make sure you don’t house them together with long-finned fish like bettas and angelfish.
Guppies (Poecilia reticulata)
|Up to 2 Years
|75-82 degrees F
In my opinion, guppies are among the most underappreciated fish in the hobby. If you have ever raised some guppies, you’d know they’re so much more than just feeder fish.
While male guppies come in dazzling colors, females look somewhat washed out and drab. Nonetheless, both sexes make active swimmers and love to dart around the tank.
Guppies are omnivores and are widely considered one of the easiest fish to feed. They will readily chow down whatever you have to offer. Besides the staple pellets and flakes, you can fortify their diet once in a while with yum snacks like peas, bloodworms, shrimp, and cucumber.
Behaviorwise, guppies are super well-mannered fish. They are active swimmers that enjoy the company of their own kind. You can say that they find safety in numbers.
The male will do a funny fin-wiggle dance to impress potential partners during mating season.
Some ideal tank mates for guppies would include gouramis, platies, ghost shrimp, and mollies.
Ember Tetras (Hyphessobrycon amandae)
|73-84 degrees F
Ember tetras are just as fascinating as their name. They sport a brilliant shade of orange-red in a gradient pattern. In the wild, they live in slow-moving waters of the Araguaia River, shadowed by heavy overhanging vegetation.
Like danios, ember tetras are omnivores as well. Therefore, feeding them is not difficult. You have an array of options to choose from. Besides the staple diet of pellets and flakes, you can treat them with frozen and live food like daphnia and brine shrimp.
They love to nibble on aquarium plants once in a while, but they pose no threat.
Ember tetras are active swimmers. Hence, they need plenty of open areas to swim in. But you also need to add a few plants and create hiding spots for them to retreat in.
These are active yet peaceful fish that don’t pick fights with anyone in the community tank.
Suitable tankmates for your amber tetras would be small rasboras, neon tetras, red cherry shrimp, dwarf gourami, and pygmy catfish.
Don’t keep tetras alongside fish with flowy fins, as they love nipping fins.
Also, avoid keeping them with large, aggressive fish.
White Cloud Minnows (Tanichthys albonubes)
|64-72 degrees F
The beautiful metallic body contrasted against the bright red tail set white cloud minnows apart from the rest. Their scales have a pretty iridescent hue, contoured by black lateral stripes.
White cloud minnows are omnivores and are not picky about what they put in their mouth at all. In fact, in the wild, they are micro predators. So you can give them microworms, mosquito larvae, algae, blanched veggies, dried pellets, and frozen food in the tank.
Like the rest from the minnow family, white cloud minnows have a very strong schooling instinct. Therefore, you should strive to keep at least 5 of them together.
While they are shy and peaceful for most of the part, they can be quite mean and aggressive when mating.
Sparkling Gouramis (Trichopsis pumila)
|75-82 degrees F
Beautiful would be an understatement when describing sparkling gouramis. They resemble shiny, iridescent bullets darting through the water in the tank. Their blue, red, and green sparkles indeed allow them to stand out in any fish tank.
Sparkling gouramis are omnivores. They primarily snack on insects, worms, and zooplankton in the wild. That’s why they require a protein-rich diet in the tank as well.
You can give them artemia flakes, live daphnia, bloodworms, and veggie flakes!
Since these fish originally come from water bodies surrounded by heavy vegetation, they’d mainly stick to planted areas of the fish tank.
They can be quite aloof and apprehensive when first introduced to a new environment, but they are inquisitive once comfortable.
The suitable tank mates for sparkling gouramis would be dwarf suckers, dwarf gouramis, dwarf pencil fish, and neon tetras, don’t pair them with aggressive, big fish.
Pygmy Corydoras (Corydoras pygmaeus)
|Up To 3 Years
|72-79 degrees F
Pygmy corydoras are also often known as pygmy catfish. Growing just around 1.2 inches long, they are one of the smallest species coming from the catfish family.
These fish sport fascinating black and white patterns, which can be quite hard to distinguish due to their trim physique.
In the wild, pygmy corydoras mainly live and scavenge at the bottom.
Therefore, you can give them sinking pellets. Since they’re omnivores, you can also fortify their diet with brine shrimp, insect larvae, bloodworms, and blanched veggies in the tank.
Temperament-wise, these fish are incredibly peaceful and tolerant of other fish in the tank. Some ideal tankmates for pygmy catfish would be zebrafish, mollies, neon tetras, cherry barbs, and dwarf gouramis.
Dwarf Pufferfish (Carinotetraodon travancoricus)
|Up To 4 Years
|74-82 degrees F
Dwarf pufferfish are among the most enduring and adored fish in the pufferfish family. Tropical freshwater fish, they look so fascinating owing to their huge eyes, petite figure, and comical expressions.
They may be small, but in the wild, they’re hunters. They mainly snack on algae, copepods, insects, and larvae in their natural habitat.
Alongside staple pellets and flakes, you can give them brine shrimp, algae wafers, snails, and bloodworms in the tank.
Apparently, these fish would prefer to lead a solitary life. But they can safely cohabitate with other peaceful fish in the tank as long as there’s enough space for everyone.
The right tank mates for these fish would be filament barbs, leopard danios, ember tetras, mosquito rasboras, and neon tetras.
Scarlet Badis (Dario dario)
|0.79 Inches (2cm)
|75-79 degrees F
In my opinion, scarlet badis are the most beautiful fish on this list. Yes, they even top bettas. The stunning contrast of orange and silver bars makes these fish look almost animated.
These fish are native to crystal clear shallow waters and the sandy gravel substrate of India’s Brahmaputra River. And they are among the smallest known percoid fish species.
Although small, these fish are predators. Therefore, their diet requires a good chunk of meaty food. In fact, many specimens are known to deter dry flakes and pellets.
Therefore, you might have to resort to giving live and frozen food like small crustaceans, insects, insect larvae, and small worms regularly.
When first introduced to a new setting, these fish are peaceful and shy.
However, aggression and getting territorial are innate and will reveal themselves sooner or later. They’re pretty intolerant of fish from the same species or other fish that look like them.
The best tankmates for scarlet badis would be pygmy corys, small gouramis, chili rasboras, galaxy rasboras, and dwarf spotted rasboras.
Endler’s Livebearers (Poecilia wingei)
|75-85 degrees F
Endler’s livebearers are small fish with a long name – reaching only around 1.5 inches long at max. They originally come from heavily planted river basins of Venezuela and would appreciate the inclusion of plenty of plants in their tank.
These fish have an interesting sleeping pattern that many find quirky. They fall asleep at the top and slowly drift down to the bottom.
Like guppies, endler’s livebearers are omnivores. They mostly enjoy devouring live/dried/frozen meaty foods. Therefore, you should often give them insects, larvae, brine shrimp, bloodworms, and daphnia.
They also eat their greens. So you can give blanched veggies like cucumber and zucchini alongside good quality flake food.
They are peaceful and social species that get along with most fish in a community tank. Just make sure that you don’t pair them with big predatory fish.
Some ideal tankmates for these fish would be guppies, tetras, honey gourami, glassfish, ghost shrimp, cherry shrimp, and cory catfish.
Frequently Asked Questions
Can Tropical Fish Live Without A Filter?
If the tank is well planted, has a low stocking number and clean water, and you constantly maintain it, your tropical fish can live without a filter for an extended period. But eventually, ammonia and nitrite will start accumulating – making the water toxic for your fish.
Therefore, I strongly recommend getting a reliable filter for your tropical fish.
How To Keep Fish Alive Without A Filter?
There are a few tricks you can pull, but there’s no guarantee that your fish will lead a happy and long life without an efficient filtration system.
Nonetheless, planting the tank heavily, performing frequent water changes, testing the water parameters regularly, and creating a favorable ground for good bacteria can go a long way to keep a fish alive without a filter.
How Long Can A Pleco Live Without A Filter?
Depending on the pleco’s health and the tank’s environment, the bottom-dwelling fish can live without a filter for anywhere between a couple of days to a few weeks.
If the tank’s environment is maintained correctly – frequent water changes, regular tests, stable temperature, and proper aeration – your pleco can go on for a reasonable amount of time without a filter.
But I’d still recommend against it. You never know what’s brewing inside the water.
Can Gouramis Live Without A Filter?
Yes, gouramis can live without a filter. But the right question to ask here is, “how long can gouramis live without a filter?”.
Gouramis are incredibly hardy fish. But they’d still struggle and suffer to a great extent if you haven’t equipped the tank with a filter. The toxic buildup of ammonia and nitrates will sooner or later take a toll on their lives.
How Long Can Neon Tetras Live Without A Filter?
Neon tetras can go on without a filter for anywhere between a few days to a couple of weeks. It all boils down to your tetra’s health status and the tank’s environment.
If the neon tetras are perfectly healthy and the tank’s environment is pristine, they can survive a few good weeks. However, if they’re in a frail state and the tank is already dirty to begin with, your neon tetras can only survive a couple of days.
Final Words: Fish That Don’t Need A Filter
Truth be told, no fish don’t need a filter in a closed system like tanks. That being said, there are a few hardy species that can comparatively go for filters for longer and are more forgiving of rookie mistakes.
All the fish I mentioned above are among the hardiest species in the hobby. Therefore, they can live without a filter for a certain duration if the tank’s environment is safe and healthy.
If your tank is dirty and polluted, no fish can survive for more than a couple of days, no matter how hardy it is.