Small tanks and bowls are great for critters like snails and shrimp, but what about fish? Can fish live in bowls and micro tanks? And do you need the whole set-up, including a filter? There are a lot of questions that beginner fish keepers have when it comes to setting up a tank and the fish that don’t need a filter. Sometimes, it is recommended to get some experience before you even attempt at keeping fish without a filter.
But if you are earnest, careful, and willing to give it a go, then you should know which fish don’t need filters and how to take care of them. With a little work, you can make that bowl or micro tank a stunning habitat for your fish.
Let’s get started.
Do Fish Need Filters To Survive?
Before we discuss the fish that don’t need a filter, it is important to talk about why you need to keep the water clean. Different types of fish have different needs, including the quality of water they swim in. Some fish needs unchanging parameters while others can make do with slightly dirtier, less oxygenated water. Bettas and goldfish are two examples of hardy fish that do not require continuously filtered water; but they do need regular water changes.
That said, all fish can benefit from a filter. If you don’t have a filter, changing the water is the next best thing. The water doesn’t have to be 100 percent pure and can come from the tap.
Keep in mind that just because your fish look fine, it doesn’t mean they are. Fish will stay afloat until they can’t. And once they keel over, they’re not going to get back up. So if you must do without a filter, be sure to routinely test the water quality for ammonia, nitrates, and nitrites. Change the water routinely. Provide plenty of live plants for oxygen.
What Kind of Fish Can Live In a Bowl?
Since bowls are the popular choice for people who don’t want a filtration system, you need to first understand that only certain types of fish can be kept in bowls. Most bowls are way too small for large decorations, plants, and other equipment. This means that the fish you keep in the bowl or micro tank also needs to be able to survive a Spartan environment.
This means you need small, hardy, cold water fish.
Hardy fish can adapt quickly. They can handle slightly toxic water for short periods of time, and they don’t need a level temperature. Small fish do not take up a lot of space and thus do not make a lot of waste either. This helps with keeping water clean. Lastly, cold water fish species won’t require a heater. They will be able to adapt to the rise and fall of the water temperature.
This does come with some caveats, though. Some fish that don’t need a filter do need a heater, like betta fish. Some fish need a minimum of 5 gallons.
It is your job to ensure that your fish are comfortable if you want them to survive without a filter.
The Best Fish That Don’t Need a Filter
Now that you know what to keep in mind when keeping fish in a bowl or micro tank without a filter, let’s talk about the fish species that are ideal for this set up.
1. Betta Fish
Yes, you will need to get a heater for your betta fish. But they can survive without a filter when you make appropriate adjustments. Aside from making sure they have warm water, betta fish are easy to care for, and they are ideal for fish keepers of all ages. While most betta fish do not get along with one another, you can keep them with passive tank mates, such as guppies or danios, if you have a smaller tank. Betta fish usually live 3-5 years.
Another great choice for a bowl or nano tank would be guppies. These hardy fish are known as rainbow fish for their brightly colored fins and iridescence. They also breed rapidly, which can be troublesome for those aquarists who keep their guppies in a smaller tank or bowl. For that reason, opt to keep guppies of the same gender together rather than mixing them up. Guppies are friendly fish and mix well with others. They grow between 1-1.5 inches (2.5-3 cm) and live for about 2 years.
3. White Cloud Minnows
These striking little fish can exist in smaller groups but do best in a minimum of 10 gallons. They are from freshwater rivers in China and have gorgeous coloring that will brighten your tank. They are considered low maintenance, peaceful, and can live up to 7 years with the proper parameters. There are three common varieties of white cloud minnows: the Golden Cloud, Hong Kong, and Meteor varieties. Their coloring and sizing might differ slightly, but for the most part, each variant can survive happily in a smaller tank without a filter. Just make sure to provide the with a pH range of 6.8-7.5 and temperatures between 64-72 degrees F (17-22 degrees C).
4. Zebra Danios
For those who don’t want to spend a lot of money on their fish but want an interesting addition should consider zebra danios. These tiny fish are resilient and very easy to take care of. They have black and silver horizontal stripes on their bodies and are often seen darting around the water or grouping together with other danios. If taken care of well, danios can live much longer than their average life expectancy of 2-3 years.
5. Salt and Pepper Corydoras
Also known as the salt and pepper catfish, these little gray and white cories are fun additions to any bowl or micro tank without a filter. They are super easy to care for, live for about 2-3 years, and require a temperature between 77-80 degrees F (25-27 degrees C). This means you will need to provide them with a heater, but otherwise, they need very little maintenance. Cories are also bottom feeders who love all kinds of foods. They do prefer to live in groups, so you should consider them for a 10 gallon tank and keep them in schools.
6. Pea Pufferfish
These little guys are an adorable addition to any micro tank. They are also known as pygmy pufferfish and are from Southwest India. Though they were once considered rare, you can now find them in pet stores around the world. They need a minimum of 5 gallons and grow to around 1.4 inches (3 cm) in length. Unlike marine pufferfish, a pea pufferfish can survive in an unfiltered tank as long as the pH is around 7-7.8 and the temperature is between 73-84 degrees F (22-28 degrees C).
7. Scarlet Badis
These cool looking fish are perfect for tanks between 5-10 gallons or larger. They are small, hardy, and grow to about 2 cm in length. Females are usually 0.7 cm smaller than their male counterparts. The main point with these fish to keep in mind is that they are predatorial. Only keep scarlet badis together. Do not keep them with smaller fish. Also, you are going to need a tank that has plenty of live plants and décor, since that will keep the tensions between the fish down.
8. Ember Tetra
With a minimal care level, an average size of 2 cm (about 1 inch), and adaptability, ember tetra are a great fish for nano tanks. They do have a minimum requirement of 5-10 gallons and require plants to be happy, but they can survive without filtration. Ember tetra are a cousin to the popular neon tetra and are native to Brazil. They have bright red-orange bodies that are slightly translucent. Try to keep the water parameters between 73-84 degrees F (22-28 degrees C) and the pH around 6.6. These are schooling fish, as well. They do best in groups. Keep this in mind if you decide on having a few!
9. Six-Ray Corydoras
Since six-ray cories will rarely grow larger than an inch (2.54 cm) in size, they are the ideal fish for a tank 10 gallons or more. Now, here’s the thing: a 10 gallon tank without a filter can be difficult to keep clean, so it’s a good thing cories are bottom-dwellers. Originating from South America, sixray corydoras need a temperature between 72-77 degrees F (22-25 degrees C) and a pH level of 6-7.2. Try to make the environment slightly more tropical in order to keep them happy. This means you might have to use a heater and provide them with plenty of plants.
Why Can’t I Keep a Goldfish In a Bowl?
A lot of people might question why there is no goldfish on the list of fish that don’t need a filter. While a goldfish can live in a bowl, it will be neither healthy nor happy. In fact, you are shortening its life dramatically.
Goldfish produce a lot more waste than you might anticipate, and because of this, they need a filtered tank. Otherwise, harmful waste products, like ammonia, are going to build up rapidly within the bowl and kill your goldfish.
Furthermore, most people don’t realize this, but an adult goldfish can grow up to 12 inches (30 centimeters) in length quite rapidly. In ideal conditions, a goldfish can also live up to 20 years! This is why buying a $0.25 feeder goldfish and keeping it as a pet is a horrible idea.
If you ignore the warnings, you are signing yourself up for multiple water changes per week and watching your goldfish suffer for maybe 2 years before it dies. Please don’t do that.
When you go to choose the fish that you are going to keep without a filter, remember this list. Not every fish is going to be able to survive without filtered water, but the ones listed here are hardier and much more resilient than other options. Be sure to provide your fish with a heater if necessary! That way, you can keep your fish for many years, even though you are not filtering their water continuously.
Good luck and happy fish keeping!
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