What Size Fish Tank Should You Get?

So, maybe you want to get your first fish tank, and have no idea what size fish tank to get. Does the size of a fish tank matter in any way?

Yes, your aquarium size plays a crucial role in determining the general health of your fish. As most aquarists put it, the bigger the better. However, the question is: how big should be your first aquarium?

What Size Fish Tank Should You Get?

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What Size Fish Tank Should You Get?

Over the years, skilled aquarists in conjunction with store owners, have assessed different situations and came up with a general rule of thumb – the one inch per gallon rule.

One Inch of Fish for Every Gallon of Water

This is probably the most widely used rule out there. On the other hand, it is the most confusing. But you can ask yourself why?

Generally, most people simply interpret this rule to basically mean, for every one inch of fish, they need one gallon of water space. Consequently, for the five-gallon tank, they will easily go for five pets featuring one-inch length each.

That is not the case. The rationing is based on cubic meters and not lengths. As your pets grow, they not only increase in length but also mass.

In fact, the change in mass and overall weight is much faster than that of lengths. So instead of length, be sure to speak more about how wider the pets have become.

Secondly, it is not all about the current fish sizes. Rather, it is more about hard-to-predict lengths of your pet when they have fully grown. And lastly, it is more about the level of the impact a specific pet pose inside your tank.

Aquarium species such as danios and tetras produce a negligible amount of wastes. On the other hand, species such as plecos and goldfish produce large volumes of wastes.

Finally, to add on top, fish tank shapes differ depending on their materiality and individual aquarists tastes and preferences.

Added to the fact that you need to integrate some tank elements such as trees, your ten-gallon tank may not be in a position to carry nine gallons of water…leave alone ten.

Bottom line, though the rule is popular among adept aquarist, as a newbie in the field, it is only prudent to stay away from it.

Things to Consider When Choosing Fish Tank

If you were keen on the one-inch rule, you must have observed that there are numerous determinants when it comes to choosing the best size tank. These factors include:

Fish species You Want to Keep

Your aquarium fish can fall under either saltwater or freshwater species. Way, the two variants fit any type of tank— whether acrylic or glass.

However, the bracket your pet belongs is key when determining its rate of metabolism, length, mass, swimming characteristic and its compatibility towards other species.

Some of the popular aquarium fish that you will often find in most tanks include:

– Goldfish



Goldfish is one of the most depressed fish worldwide. Yes, you will often see them caged in colored bowls with no adequate swimming environments.

Under an appropriately sized aquarium, goldfish can grow to an average length of about 5 inches.

In the wild, they grow to an unimaginable size of about 15 inches.

So if you do not want to stunt the growth of your goldfish and decrease its shelf life, then go for a big tank.

Never keep a goldfish in a bowl or in a small tank!

– Guppies

Guppy Fish

Guppy Fish

Guppies are social species of fish known for their beautiful colors, active behavior and small size of about 2 inches.

They can easily fit the small and medium-sized tanks around.

It is not recommended to only keep one guppy, so you will want to keep at least 3-4 together.

Considering this fact, you will want to get at least a 5 gallon aquarium, but best would be a 10 gallon tank.

– Neon Tetra

Neon Tetra

Neon Tetra

Neon Tetras are second in the list of most popular species worldwide.

Just like guppies, they feature small-sized bodies of approximately 1.5 inches in their adulthood.

For one tetra, 1-2 gallon of tank water is enough, but there are few things to consider here.

Neon tetras (and other tetra fish types), are schooling fish. They are happy in a school of 5-6 fish. Additionally, they swim a lot back and forward.

That said, if you want to keep your neon tetras happy, get at least 5 fish and at least a 5 gallon aquarium for them.

– Betta Fish

Betta Fish

Betta Fish

Betta fish come in small size in the stores but grows fast within no time.

If you are a frequent visitor in fish stores, you will observe that bettas are often confined in very small containers.

However, when bettas reach their adulthood, they grow to about 4 inches in length. They will also, in that phase of life, need more swimming space.

While many consider that a 2.5 gallon aquarium is enough for a betta fish, I personally recommend at least 5 gallon tank for your fish.

– Zebra Danios

Zebra Danio Fish

Zebra Danio Fish

Danios are full of life and very active. They fall in the bracket of best swimmers worldwide.

A fully grown zebra danio measures approximately 2 inches in length.

For each danio, you may need approximately 2.5 gallons of water.

Zebra danios feel comfortable in a school of 5-6, so that means, that you will nee at least a 13 gallon tank for them.

Fish Tank Maintenance

Fish Tank Maintenance

Fish Tank Maintenance

Your aquarium takes after a pond environment. You need to alternate the parameters to maintain a healthy water condition.

However, the state of your tank water hardly matters. Rather, it’s the state of your pet’s lives.

A small size tank holds a small volume of water. Consequently, your water parameters can whack out any time of the day whenever you don’t take caution early enough.

It cannot easily achieve a stable environmental condition for two days successively without the need to change your waters.

On the other hand, a large volume of water acts as a large pond. Wastes generated in the form of excrement and food leftovers diffuse and get diluted in the water without any potential risk to swing in parameters.

With a big tank, you do not need to change your water as frequent as with a small tank.

Your Budget

Just like any other form of pet-keeping, you need to work with a practical budget when setting up a new tank.

First, your budget should accommodate all the expenses you are going to incur right from the purchase of a new tank. Additionally, it should be flexible enough to accommodate any other expenses that you might have not considered when planning.

In reality, a big tank widens the scope of your budget. By installing a bigger aquarium, you should be on budget with additional accessories such as a bigger heater, more filters and more water conditioning treats.

Additionally, where there is not enough space for the tank, you will need to work on some establishments before hitting the road. All these relate to the added cost.

Otherwise, in the middle of the journey, you will realize that a bigger tank cuts on the costs relating to the frequent change of water and pH maintenance.

Acrylic or Glass Fish Tank

Most of the tanks that many aquarists have feature either acrylic or glass materiality. Both variants are unique and better depending on individual aquarist preferences and expectations. However, the materiality aspect affects both the budget and size of an aquarium to carry home.

First, an acrylic tank features fine aesthetic appeal. They are not only expensive but also easy to scratch. Even with that, they still guarantee an effortless view of the pets inside without the need to strain.

On the other hand, glass tanks are heavier and much more expensive to transport as compared to acrylic. Additionally, larger glass tanks of more than 200 gallons are a bit expensive when compared to acrylic counterpart.

Quite unbelievable..! But, the reality on the ground is that the larger the surface area of glass used, the more dollars you will use for its purchasing.

Therefore, for small and medium-sized tanks of 2 gallons to 100 gallons, it will be wise to purchase a tank aquarium. On the other hand, for sizes ranging from 150 to 1000 gallons, go for acrylic.

Oxygen Dissipation

Fish survive on dissolved oxygen in the tank. The dissolved oxygen dissipates through an open surface created mostly at the top of your tank.

Your tank may be large enough but may not have enough space to allow oxygen to dissolve. As a result, you may wake up to dead pets floating on the surface of your water.

The basic truth is that size hardly affect your tank’s efficiency. Rather, it is the surface area of the water exposed to freely-moving air.

This is why fishbowls are very dangerous for fish. When they are filled with water, the surface area is reduced significantly and oxygen exchange as well.

Therefore, asses the tank’s opening carefully before deciding on the best tank to carry home.

Why are Bigger Size Fish Tanks Better?

Why are Bigger Size Fish Tanks Better?

Why are Bigger Size Fish Tanks Better?

As mentioned earlier, bigger fish tanks are better thanks to their large water volume. Bigger aquariums are more stable in terms of water chemistry and temperature change.

If there is an ammonia spike in the aquarium (which can be deadly for fish), a larger water volume will “handle” it easier, than a smaller one.

If you want to keep aquatic plants, there will be less work with a big tank, because it has more room for the plants to grow, and will not require often plant trimming.

You can also skip on water changes. A big stable fish tank (over 50 gallons), will not require as frequent water changes as a smaller one. This is only true, however, if it is not overstocked.

Does the Aquarium Size Determine How Large a Fish Will Grow?

Yes, aquarium size can determine how large a fish will grow. Also, the size of the aquarium will greatly affect the growth speed of the fish.

For example, guppy fry will grow slower in a small aquarium. On the other hand, it does not mean, that the bigger the tank the larger the fish will grow.

Each fish species have its own genetics, which will determine the maximum size of the fish.

What is the Best Size Fish Tank for Beginners?

So, which size fish tank is best for beginners? Personally I recommend a 10 or 20 gallon fish tank for beginners who are just starting out.

This will give you stability in water parameters and you will learn how to care for your fish. The risk is low, because you will not need to care for hundreds of fish, just for 5-6 at a time.

Don’t worry if you will make mistakes, I also made lots of mistakes when I started with my first tank.

As a beginner, it would be best to choose an aquarium kit, because this has all the equipment you need. I recommend the Aqueon 10 Gallon Kit and the Tetra 20 Gallon Kit. You can purchase both online from Amazon.

Wrapping Up

If you have reached this point, then there is no doubt that you have known what to go for.

The bigger your tank, the better is its conditioning. And, the easier it is to maintain.

If you have any questions, please leave a comment below and I will do my best to answer it quickly.

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