How Many Fish Can You Keep In A 2 Gallon Fish Tank?7 mins read

Fact checked by
Tal Halperin
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How many fish can you keep in a 2 gallon fish tank
Image from pinterest

A 2 gallon (10 liter) fish tank is a popular alternative to larger tanks, whether that’s because you only have a small space, a low budget, or simply because you like the look of these little tanks. But with such a delicate size, there are some careful considerations to take into account – such as the optimum number of fish for this kind of tank.

This guide will go into suitable species for a 2 gallon nano tank as well as the best number, keeping conditions stable, school dynamics and more. A 2 gallon tank definitely isn’t suitable for all kinds of fish, but providing you have done your research, there’s no reason you can’t set up a thriving nano aquarium – so read on.

How Many Fish Can Fit In A 2 Gallon Fish Tank?

The absolute answer to this is, a maximum of four or five. A 2 gallon fish tank is an unusual and cute little tank and can be very tempting for beginner aquarists, but unless you know exactly how to set one of these up, you’ll find it’s not very helpful for your or your fish.

These tanks might look cute, but it’s important not to just stick fish in a tank and leave it at that, so this guide will explore the magical number of four to five as well as some aspects of fish lifecycle and behavior to show you how you can make a 2 gallon tank work and why it’s important to always keep fish in groups – so read on.

What Is A 2 Gallon Fish Tank?

A 2 gallon fish tank is exactly what it says on the tin – a small tank that has only two gallons of water capacity. This kind of tank is very visually appealing, and is also known as a nano tank.

Why might you want a nano tank? There are a couple of reasons these tanks appeal to both new and experienced aquarists alike, including the following:

  • Nano tanks are great for small spaces. Do you have a tiny apartment where the only room for a tank is on a desk or other crowded surface? A nano tank is often touted as the answer.
  • They are easier to clean and maintain – it’s a no brainer, but a tank with less water means less difficult water changes and less carrying buckets of dirty water around the house to dispose of them.
  • They are easy to filter. You don’t need to use up a lot of electricity to run a filter for a nano tank. Thus, they are very appealing for fishkeepers who don’t want the cost of running a setup that uses lots of electricity.
  • They look cute. Last but definitely not least, these are cute and quirky tanks that appeal because of their diminutive size and unique nature. However, it’s always important to consider factors beyond just looks for any fishtank.

Are Nano Fish Tanks Good For Fish?

Are nano fish tanks good for fish?
Safely keep a school of fish in one of these tanks you may find yourself investigating smaller species that are less common or popular in the aquarium trade. Image from pinterest

You may have heard horror stories and wonder whether they can ever be healthy or suitable for housing fish.

Don’t worry – these tanks are not 100% bad and they can be great for a small aquascape with suitable fish. However, the myth of being able to keep a single species of larger fish in these tanks is exactly that – a myth.

Is It Ever Possible To Safely Keep Fish In A Nano Tank?

The species that you can keep safely in a nano tank tend to be small schooling fish – but we’re talking small here. Even some fish that are commonly put in this category like some kinds of tetras and Zebra Danios will not thrive in a 2 gallon aquarium as they need to be in groups and there simply isn’t room for a suitable group number.

Therefore, to safely keep a school of fish in one of these tanks you may find yourself investigating smaller species that are less common or popular in the aquarium trade. Nevertheless, this can actually open your eyes to a new world of tiny and mesmerizing companions, making your tank a little different from the average aquarium.

Best Fish For A 2 Gallon Fish Tank

Are you wondering what are the best fish for a 2 gallon fish tank? The fish that are best suited to a nano tank are those that are even smaller in size than most common small dither fish (Zebra Danios, Tetras, etc) such as rasboras, one of the smallest members of the Carp Family.

Fish For 2 Gallon Tank – A Selection

The following species will give you a good idea of what fish are suitable as most of them don’t grow much over one centimeter.

How To Set Up A 2 Gallon Fish Tank

How to set up a 2 gallon fish tank
It’s good to keep a test kit on you at all times for both toxins and pH. The small size means conditions across the whole tank can deteriorate rapidly. Image from pinterest

Setting up a 2-gallon fish tank isn’t that much different from any other tank. However, it’s good to pay special attention to the spot and conditions your tank is exposed to. This is because due to the small size, there is an increased opportunity for stressors to your fish. Therefore you want to minimize these as much as possible.

Apart from this, here are some things to consider if you want to keep fish in a nano tank. If you take these into account, you can inevitably keep up to four small fish in a 2-gallon aquarium:

  • Your tank will need a filter and potentially a heater. You will have to ensure these are suited to a nano tank otherwise they may be too strong.
  • It’s best to keep your tank out of bright and direct light. The main difference between a 2-gallon tank vs a 30-gallon (114 liter) tank is there are much fewer places for fish to hide and shelter. LED lights are too strong for many species without any place to hide.
  • A nano tank is not a contained ecosystem, it is not self filtering, and you definitely can’t leave it without testing for nitrates, nitrites, and ammonia.
  • It’s good to keep a test kit on you at all times for both toxins and pH. The small size means conditions across the whole tank can deteriorate rapidly.
  • It can be helpful to change the tank water more than once a week. Remove a third and replace with fresh as with a normal tank. Changing it once on the weekend and once midweek can be a huge benefit to both you and your fish as it keeps things crystal clear.

Does A Nano Tank Need Any Special Considerations?

Beyond understanding the needs of the fish and plants you include, a nano tank does not necessarily need any special considerations. However, you may be wondering what is the best 2 gallon fish tank filter.

2 Gallon Fish Tank Filter

As you have a very small space without much room for water to flow, it’s imperative you don’t use a strong filter. This could injure your fish and disrupt the delicate tank environment.

Fortunately, there are products on the market specifically for nano tanks. A good example of a filter that is designed especially for aquariums under 4 gallons is the Tetra Whisper Internal Filter. It’s unobtrusive and won’t be too strong for your small tank.

Planting And Decorating A 2 Gallon Fish Tank

Now you have the practical parts of your tank set up, you will want to plant and decorate! Bear in mind the amount of fish you are keeping in your tank/ If you have a larger group (around 5) as opposed to smaller (4) you may need fewer plants. Most of the common aquarium plants found in larger tanks are too big for a nano tank. However, there are some creative solutions that you may find just as appealing.

Best Plants For A Nano Tank

The best plants are small and unobtrusive floating plants. Duckweed, mosquito fern, and dwarf water lettuce can all be floated on top of a nano tank, ensuring that there is something extra to filter nitrates and nitrites.

On top of these, these other species are also great for a small tank:

How To Ensure Plants Thrive In A Nano Tank

Plants in a nano tank have the same needs and considerations as plants in any other kind of tank. They all need sunlight and nutrients but not too much. In a nano tank, adding a light can sometimes be too bright for both fish and plants, so this is one thing it’s potentially best to avoid.

Otherwise, plants will thrive taking in the nutrients from your fish’s waste. You can add a soil substrate but bear in mind due to space constraints you may not have much room. Alternatively, you can stick to floating plants or plants that are weighted down.

Common Problems And Troubleshooting In A 2 Gallon Fishtank

Common problems and troubleshooting in a 2 gallon fishtank
This is a major issue in small tanks and is one of the main causes of fish mortality. Image from pinterest

Even if you’ve done your research, there can still be problems that occur with a nano tank. As a result, it’s helpful to know how to handle these when they arise.

1. Fish Don’t Get Enough Oxygen

This is a major issue in small tanks and is one of the main causes of fish mortality. If you have too many fish, the tank is polluted, the filtration isn’t strong enough, or there isn’t enough surface area, fish can die from lack of oxygen as they are unable to get it from that water.

Luckily it is easy to spot, as you may see their gills working harder than usual and they may have trouble swimming or seem in distress.

In the first instance, you should change the water. Remove a third of the water and replace it with fresh. In a nano tank, it can help to do this the day after too just to help get conditions back to normal.

However, if the problem persists it may be you have too many fish in your tank and you may have to upgrade.

2. Fish Are Fighting

Similarly to fish not having enough oxygen, this can arise when your tank is too small or you have too many fish in the tank.

Fish fight for many reasons including over mates, food, and territory, however, in a nano tank, it’s most likely this will be over territory.

It’s always best to change the water first or test for the presence of toxins but if this happens, it is a major sign you have too many fish.

3. Plants Are Dying

This isn’t always a common problem in nano tanks because plants will thrive on your fish’s waste, which will be highly concentrated in such a small environment.

Plants can die for many reasons. Too much heat, not enough light, or alternatively too much light can make their leaves turn brown.

Alternatively, if you have too many plants in the tank they may be competing with each other. Overgrown conditions can make plants more susceptible to disease and you may see leaves and roots turning black due to this being a good set of conditions for bacteria.

4. Water Is Cloudy

This is exactly what it looks like – a sure sign that your tank is dirty, as the cloudiness is generally fish waste.

If your fish haven’t started struggling, if you see this, it’s always best to change the water while things are still good in the tank.

You can change it the subsequent day too just to give things a boost and get water conditions back to optimum.

Bottom Line

A nano tank may look lovely but it definitely takes a little bit more attention and upkeep than a regular tank. Like a hexagonal fishtank, it is a fantastic unusual aquarium but making sure you are informed ensures you will know how to maintain it to keep conditions at their very best – and deal with anything that happens.

Additionally, a smaller tank can help you learn about species you may not otherwise consider. It’s a great way to stop and focus on the environment you are setting up, and as a result it can be an attractive and calming feature of any small desk or tabletop.

Frequently Asked Questions

Is it possible to keep snails and shrimps in a nano tank?
Not only is it possible to keep snails and shrimps in a nano tank, they are actually a recommended alternative if you don’t want to keep fish, or if you can’t find fish that are small enough Many species of shrimp and snail do not grow very large but can still be striking and colorful. For example, cherry shrimps have an eye-catching red color, whereas ghost shrimps are, like their name suggests, see-through. In addition, shrimps and snails have different social behaviors to fish, so you don’t necessarily need to keep them in as large a group.
Are nano fishtanks cruel?
When set up correctly, a nano fish tank doesn’t have to be cruel. However, if you don’t keep the right kind or number of fish, it can lead to very inhospitable conditions. However, if you’re open to more unusual species, or invertebrates, then there’s no reason why you can’t keep the right fish in a nano tank.
Is a two-gallon aquarium suitable for a Betta Fish?
One species you should never keep in a nano or 2 - gallon aquarium is the betta fish. At first, it may seem perfect as males of this species are solitary. However, a betta fish must be kept in a tank that is a minimum of 5 to 10 gallons. You may see betta fish kept in tiny tanks in the pet shop - a process known as jarring. However, this is just intended to prevent males from fighting each other or turning aggressive towards other species. It’s not intended as a permanent home, only a temporary measure before the fish go home to a larger aquarium.
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Tal Halperin

Tal is an avid fish keeper and has been raising ornamental fish for decades. As a little boy, he drove his father crazy to buy him an aquarium with all the necessary equipment. Now, after a career in the field, he has set up Your Aquarium Place to offer the most comprehensive guide to ornamental fish keeping available and share his passion for the different species he has looked after.