Even though fish tend to be a low maintenance pet, they still need a good home to keep them happy. When buying a fish it is important to consider what size tank is good for your fish and good for your home. Here is what I have found about finding the right sized aquarium for you.

What size fish tank should I get? The bigger the tank the better. For most common freshwater fish, it is recommended that you have a 10-gallon tank per fish, with the dimensions of 22” x 12” x 13.5”. For most common saltwater fish, it is recommended that you have a 30-gallon tank per fish, with the dimensions of 36″ x 18″ x 12″.

This is only an overview of what goes into making sure you have the right sized tank. If you are interested in a more in-depth guide on finding the best fish tank for you and your fish, keep reading.

Aquarium Sizes for Common Freshwater Fish Species

There are many great and popular fish species that people enjoy having as pets from tropical fish to freshwater fish, from big fish to small fish the possibilities are practically endless. One thing that many fish owners forget to consider is if the size of their tank is adequate for their fish.

I have spent time learning about the best fish tank sizes for different common freshwater fish. Here are the best sizes for 5 of the most common freshwater fish.

Freshwater FishSize of FishGallons in TankDimensions of Tank
Neon Tetra1.5 inches1 gallon7.50″ x 7.50″ x 10.25″
Beta Fish3 inches2.5 gallons12″ x 6″ x 8″
Goldfish5 inches10 gallons20″ x 10″ x 12″
Guppies2 inches1 gallon7.50″ x 7.50″ x 10.25″
Zebra Danios2 inches2.5 gallons12″ x 6″ x 8″

Freshwater fish tend to be hardier, easier to take care of, and don’t require as large of tanks as saltwater fish do, making them more popular pets among fish owners. These are some of the most popular freshwater fish species for pets.

1. Neon Tetra

The first fish I’m going to go over is the Neon Tetra fish. These are very popular fish to have as pets, as they are very small only growing to be about 1.5 inches in length, and not requiring much room to be happy. Each Neon Tetra you have requires a tank that holds 1 gallon, but Neon Tetras are schooling fish, meaning they are happiest when they have more of their kind around.

It is best to have at least 5 or more Neon Tetras, to maximize their well-being, that being said a 5-gallon tank would be the minimum tank requirement. A gallon added for each fish added.

2. Beta Fish

Next popular freshwater fish for a pet is the Betta Fish. These fish are often kept in very small containers in pet stores, so people will think they don’t require very big tanks, but that is not true. Betta fish can grow to be up to 3 inches and need plenty of room to swim around.

Betta fish are usually kept alone, so a 2.5-gallon tank would be a good minimum size for one Betta. If you are going to get more Betta, it is important to only have one male, as males can get aggressive toward one another, and to increase the tank by 2.5 gallons for each Betta you plan on getting.

3. Goldfish

When many people think of pet fish, they think of a goldfish in a small fish bowl. This is not a good home for a goldfish. Goldfish need very large tanks, at least 10-gallons per goldfish. A common misconception is that Goldfish grow to their tank, but this is not true. Being in a small tank actually stunts the growth of goldfish, which is very unhealthy for them.

Goldfish in captivity can grow to be an average of 5 inches if given a big enough tank, but in the wild, they have been known to grow up to 14 inches. If your goldfish is not getting as big as 5 inches, they probably need a bigger tank. For each goldfish you have, you should increase the tank by 10 gallons (5 goldfish should have a 50-gallon tank).

4. Guppies

Guppies are a lot like Neon Tetras when it comes to the housing they need. They are small fish only growing up to about 2 inches in length, meaning individually they don’t need more than a gallon tank to be fine. But like the Neon Tetras, they are schooling fish and will feel much happier, safe, and secure with a big group to swim with.

It is recommended that you have at least five guppies together so that they are able to school. That means at least a five-gallon tank, but the bigger you are able to give them the better.

5. Zebra Danios

Zebra Danios are also popular fish to keep as pets. They are small only reaching about 2 inches when they are fully grown. They love to swim, so the bigger the tank, the happier they will be, but the minimum tank sized required is 2.5 gallons per fish.

Zebra Danios are also schooling fish, so a group of at least 5 is recommended, meaning a 12.5-gallon tank is required for these fish. If you can not find a 12.5-gallon tank a bigger size is ALWAYS better than a smaller size.

Aquarium Sizes for Common Saltwater Fish Species

Next, are the saltwater fish. Saltwater fish typically aren’t as popular as normal household pets, because they are more high maintenance and require a bigger tank, which isn’t ideal for someone with less room in their home.

Why do Saltwater fish need bigger tanks? Fishkeeping World says, “Saltwater cannot hold the same amount of oxygen as freshwater. Research suggests that seawater contains only around 80% of the oxygen that freshwater does.

So what does this mean for your aquarium? It means that with the same sized freshwater and saltwater tank, the saltwater tank has 20% less oxygen in it.

Simply put, you can’t keep the same number of saltwater and freshwater fish in the same sized aquarium because there isn’t enough oxygen in the water for saltwater fish. The saltwater fish would simply run out of oxygen.”

I have also spent time learning about the best fish tank sizes for different common saltwater fish. Here are the best sizes for 5 of the most common saltwater fish.

Saltwater FishSize of FishGallons in TankDimension of Tank
Clownfish3 inches30 gallons36″ x 18″ x 12″
Six Line Wrasse3 inches30 gallons36″ x 18″ x 12″
Green Chromis3.5 inches30 gallons36″ x 18″ x 12″
Auriga Butterflyfish9 inches125 gallons72″ x 18″ x 21″
Yellow Tang7.9 inches75 gallons48″ x 18″ x 21″

1. Clownfish

Clownfish are one of the most popular saltwater fish to have as pets, and can be found in just about any saltwater tank. They became increasingly popular after the movie Finding Nemo. They only grow to be about 3 inches, but they need a tank of about 30 gallons.

Clownfish love to hide places, and live in sea anemones. If you get a sea anemone for your clownfish, you will need to compensate with a larger tank of about another 30 gallons, making it a total of about 60 gallons.

2. Six Line Wrasse

Next fish is the Six Line Wrasse. These are also very popular saltwater fish to have as pets. They have very similar housing needs as the clownfish does. They grow to be about 3 inches in length, and each one requires a 30-gallon tank.

These fish are fairly easy to care for and can be kept with most other saltwater fish, they do not necessarily need any special treatments or needs.

3. Green Chromis

A Green Chromis is one of the most popular saltwater fish. They are very beautiful and peaceful fish. Much like the clownfish and the six line wrasse, they need to be kept in at least a 30-gallon tank. They grow to be about 3.5 inches and can live peacefully with other saltwater fish.

They don’t need to be in schools, but if you are planning to get more than one Green Chromis, you need to get at least 6 or more to keep the pecking order under control, as any less will result in the Alpha-fish taking out the smaller ones. This means if you are planning to school the Green Chromis you will need a 180-gallon tank for them.

4. Auriga Butterflyfish

The Auriga Butterflyfish is a very beautiful and popular saltwater fish to keep as a pet. They are usually only kept in very large aquariums as they grow to be about 9 inches long and need 125 gallons to be happy.

This is why many average fish owners do not keep Auriga Butterflyfish, they are more ideal for larger aquarium displays in offices or hotels. They do not need to be schooled, but they do enjoy having places to hide.

5. Yellow Tang

Lastly is the Yellow Tang. This is also a very popular saltwater fish as it is often times found in a lot of saltwater tanks and aquariums. The Yellow Tang grows to be about 7.9 inches. They need a tank that is a minimum of 75 gallons to survive and be happy and healthy.

Aquarium Sizes for Different Size Homes

Aquarium sizes for certain homes aren’t as tricky as aquarium sizes for fish, as it is more based on personal preference rather than anything else. Here are some tips for different sized houses, and types of homes that can help you in deciding what sized tank is best for you.

First is tips for small homes and apartments.

The first tip I can give you is to aim for freshwater fish. A smaller space means a smaller tank, and saltwater fish need much bigger tanks than freshwater fish do.

A good sized tank for a small house or apartment is about 10 gallons. The dimensions come out to be about 20″ x 10″ x 12″. This size can hold one goldfish or a couple of smaller freshwater fish such as Neon Tetras or Guppies.

It is important to be careful when getting a fish tank in an apartment especially if you aren’t on the first floor, as fish tanks can get really heavy and potentially break through the floor, or leak and cause water damage. This is why I believe a 10-gallon tank is ideal as it is big enough for certain fish and isn’t big or heavy enough to cause problems.

Here is a link to a great example of a 10-gallon tank from Amazon that is ideal for small houses or apartments.

Next is tips for big houses or offices.

If you have a large enough space for just about any sized tank, then it is really up to personal preference for what size tank and what type of fish.

It is important to remember not to overcrowd the tank, especially with saltwater fish as they often need more room than you think. Make sure to do your research to ensure that you are giving the type of fish you need enough room to thrive.

Things to Consider About Size Before Buying a Tank

It is important to decide which type of fish you want, and how many fish you want before buying a tank. That way you can plan out exactly how big you need the tank to be, and if you need to reconsider the type or number of fish you want to get.

Many fish owners will buy the tank or aquarium before they think about the type or number of fish they want which is the opposite of what they should do. You should be buying a tank to fit your fish, not putting your fish in any random tank you happened to get.

Fish need big tanks, their minimum tank requirement is not a suggestion, it is something that was put into place to ensure their health and happiness. Fish that are in too small of tanks will be stressed, anxious, and even become aggressive due to the stress and anxiety they endure in a small tank.

Being in too small of a tank can even kill the fish. Small tanks can stunt the growth of a fish, making it so their organs don’t have enough room to grow causing their organs to potentially fail.

The reason you need to have a certain amount of gallons for each fish is it’s possible for the fish to run out of oxygen.

“Less water means less oxygen in the water. Limited water surface in a small tank also can prevent enough gas exchange from taking place between the water and the atmosphere. Fish will die from not enough oxygen.”

Pet Keeper’s Guide

Be cautious and aware when buying fish and a tank. Take into consideration if you have the room and resources for the tank required for the amount or type of fish you want.

Related Questions:

Are bigger fish tanks easier to manage? Bigger fish tanks are typically better for beginners and easier to manage because it is easier to keep the water stable. If something goes wrong in a smaller tank, it will spread a lot faster and be harder to catch and take care of.

Can saltwater and freshwater fish live in the same tank? Saltwater and Freshwater fish can not typically live in the same tank. There are a few fish that can survive in both saltwater and freshwater, but overall one fish species will most likely die off because of either too much salinity in the water or too little.