Best Aquarium Size for Beginners – Small or Big Fish Tank?

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Are interested in buying your first aquarium to get started with fishkeeping? Or you plan to buy one for your children? Whatever your reason is, purchasing an aquarium for the first time comes with many challenges.

Probably the most important factor that goes into buying the best aquarium is its size. How can you tell what aquarium size is best for a beginner fish keeper? This is what this article is about.

I will give you a thorough guide on how to choose the best size for your new aquarium, and what you must look out for when purchasing it.

Setup Your First Aquarium

You may think that when buying a new aquarium, a smaller one is best since you’re only just a beginner at fishkeeping. But is that really true? Well, think about it!

If you buy a smaller tank, that means your fish will have a smaller environment where they will live. For them to be happy and thriving, you need a big enough aquarium.

That’s because I’m not talking about a singular fish in a small container. When you buy multiple fishes, you need to make sure the aquarium’s size is best suited for them.

For instance, most of the fish you buy for yourself are still quite young. Simply, that’s what shops are selling. So, if you buy a number of these fishes to put in your new aquarium, you must make sure the tank is big enough even when the fish grow to full size.

Many people mislead themselves into thinking that a small tank will be just fine for a number of young fishes. But don’t forget, they will probably grow in size, and the tank you bought some time ago, won’t be enough for them to thrive in.

Also, there is another factor that makes a larger fish tank better for beginners. This is something that happens, no matter the type or number of fishes you’ll have.

Every aquarium has to be kept clean from all solid, chemical and biological debris. If you have a bigger tank, it will get dirty way harder, than a small fish tank. After all, a larger volume of water, means a larger period of time to get soiled.

If you buy a small aquarium, the water could get totally soiled in a matter of days. Especially if you have multiple types of fishes living in it. So, opting for a larger tank is better to keeping it clean easier.

The third aspect that needs to be considered, is the fact that a smaller fish tank will require a much better expertise at keeping a good water balance. It’s quite logical. A big aquarium will get loaded with harmful substances a lot slower. This takes place just like the previous aspect I mentioned.

But does this mean that you have to buy a big aquarium, no matter the circumstances? No, not really.

Smaller or Bigger Fish Tank?

When you have to choose between a smaller or a bigger fish tank, there are at least 3 important aspects that need to be considered. Let’s talk about each of them in separate:

The Fish

The first factor that weighs a lot in this matter is the type of fish you plan to put inside the aquarium. Let me explain why:

For instance, if you choose to buy a fish that grows bigger when it matures, you will naturally need more room for it. But for a smaller fish, that won’t grow too big even at maturity, you don’t necessarily need a huge fish tank.

However, this is not always the case. That’s because even small fish could need a big fish tank to thrive in. There are breeds that are known to swim around all the time, and like to do more distance than others.

If you buy a group of such fishes, you also need a bigger fish tank to accommodate them. One of the species that is known for this behavior is the Tiger Barb.

This fish breed is well-known to swim a lot all the time. And on top of that, you can’t have only 1 or 2 in the aquarium. That’s because if you don’t buy at least 5 or 6 of them, they will start hurting the other fish inside the tank.

That’s just how they behave. A small group is necessary in their case to ensure the well-being of the other species in the tank.

This was only an example, but I think you get the point. Different fish breeds, need different sized aquariums. So, before you buy an aquarium for the first time, you should know what type of fish you plan to put in it.

When you know that, do some thorough research on what they need, and how they behave in a normal environment. This way you’ll know for sure the size of the fish tank that’s best suited for a specific specie.


This factor might be a natural for many people, but you should consider multiple things when you think about the costs.

A bigger aquarium will cost more money (obviously) than a smaller one. By this I mean the purchase of the tank itself. But there are other costs that need to be considered too.

Any aquarium will need a water filter that’s crafted to work specifically with the size at hand. For instance, there are filters that work well with a 10-gallon fish tank. But if you try to install it on a bigger aquarium, it will be overwhelmed quickly.

Such a device can costs more depending on the size of the aquarium you need it for. One that works with a 10-gallon tank is naturally cheaper, than another for a 20-gallon tank.

Also, every filter device needs regular cleaning and maintenance. This includes the purchase of new filter media, that has to be done regularly, to ensure a clean water and a good nitrogen cycle.

There are fish breeds that need to live in warmer waters, because of their nature. If the temperature is something you can’t achieve just by leaving the aquarium in a warm place, you might have to buy a water heater as well.

So, the point is, there are lots of aspects that you have to consider when it comes to purchase and maintenance costs.

If you feel that you can’t afford a big aquarium, a smaller one is still a good choice. However, as I pointed out above, keeping the water quality at its best is harder in a small fish tank.

Where to Place It?

You might want a bigger aquarium, but do you have enough space to put it inside your home? There are multiple things you have to consider regarding the place where the aquarium is planned to sit:

  • Is it out of direct sunlight? This is important because direct sunlight can greatly affect the water temperature inside the fish tank. If you have fish that don’t like warmer waters, it’s best to keep the aquarium out of direct sunlight.

Also, the sunlight can speed up the growth of algae that will impact the look, and more importantly health of your aquarium.

  • You have to choose a room that is silent enough for your fish. Why? Most fish don’t like loud noises and they especially don’t like to be bothered all the time by outside effects. So, choose a room where they can sit peacefully and feel at home.

If you have a place that checks all the requirements from above for a bigger fish tank, why not buy one?

But if you don’t have a big enough space for achieving these requirements, better go for a smaller tank. This way, your fish won’t suffer because of direct sunlight or loud noises or any other outside elements.

Now, let’s talk about some of the pros and cons for small and large fish tanks:

Small Aquariums

The first pro that comes to most people’s mind, is the budget. And this really is a positive. Like I mentioned above at the Financials section, a smaller fish tank is more budget friendly than a big one.

Also, a smaller tank won’t require as much money to keep up as a big one. After all, you’ll need a smaller water filter as well, with less filter media. So, you won’t spend as much for a small tank, than you’d do for a bigger one.

The second pro that’s present in the case of small fish tanks, is the ease of installation. Setting up a small aquarium is easier, than a huge one. Quite obvious, really.

But don’t mistake this with the maintenance works. That is a totally different story.

You need less materials for a small fish tank, like less vegetation and environment building items. A big tank needs a lot more of these things.

Also, a small fish tank is available for pretty much anyone to have. This is the 3rd pro that’s worth mentioning. It doesn’t matter who you are or what you do, a small aquarium will probably fit in your home, or your office.

And even places that prohibit animals, usually don’t count an aquarium in this category. So, if you’re a student, where they don’t allow animals inside, a small fish tank is probably granted.

However, there are cons as well, with owning a small aquarium, instead of a big one.

For start, a small fish tank is harder to maintain. Like I pointed out above, dirt and all sorts of harmful substances will gather in the tank quicker than in a huge aquarium.

You will need to do maintenance work a lot more frequently. This includes the clean-up of the filter, but not only. When the water gets too dirty, you’ll have to change it. And this could happen quite often.

Also, toxins could accumulate in a matter of hours, if you don’t monitor the aquarium closely at all times. This is due to the small volume of water that sits inside the tank.

Another negative that comes with small aquariums is that you can’t have a lot of fish inside it. Most small aquariums only support a handful of fish, and you can’t expand them later.

This is why going bigger from the start might be a better idea, if you have the means for that.

Big Aquariums

Now, let’s see what the pros and cons are in the case of big aquariums. When I say big aquarium, I mean those that contain about 30 gallons of water, or even more.

The first advantage of big fish tanks, is the maintenance they require. I think you saw from above that a small tank is harder to maintain. But a big fish tank needs less care, because all the waste and toxins will accumulate way harder, than in a small container.

If you don’t have a lot of time to put into maintaining the tank, a bigger one is probably a better idea. However, that doesn’t mean it doesn’t require any maintenance.

You still have to change the water regularly and clean the filter as well. The difference is that the time spent between one maintenance work and the next is way longer than with a small aquarium.

A second advantage that comes with all big fish tanks is the possibility that it gives you. What do I mean by this?

If you start out with a small tank, you can’t grow it further; you’d have to change the tank for a bigger one. This isn’t the case if you buy a big aquarium from the beginning.

If you purchase a 50-gallon aquarium, you can easily expand it with more fish and other sea life. At first, you probably won’t put a lot of fishes inside it.

But later, if you want to buy more fish that work well with the ones already inside, you can do that easily. They will have enough room to swim around and feel comfortable in their environment.

The third advantage of a big fish tank, is the fact that the water chemistry is easier to keep at the same level. Certain fish need certain resources to grow and thrive.

A bigger aquarium will keep the water’s properties for a longer time, thus letting your fish grow and thrive in this new ecosystem.

A downside of a big aquarium is the pricing. Like you’d expect, bigger the aquarium, bigger the price. If you don’t have the money for big sized fish tank, you might need to consider a small one that fits your budget.

Also, the accessories needed for the tank are more expensive too. For instance, a good water filter for a 50-gallon tank is not as cheap as another for only 20 gallons of water.

The second negative about big fish tanks is that they need much more space to put them in your room. If you live in a small apartment, you might not have the space to fit a big fish tank in a tiny place.

Besides these 2 negative aspects, a bigger fish tank is mostly a better idea, than a small one. But it really depends on your personal needs and expertise.


Let’s recap quickly what we discussed in this article:

First, we talked about the fact that most people when starting out, think that a small aquarium is better than a big one. However, I gave you multiple reasons why that’s not exactly true. A beginner will maintain a big fish tank way easier than a small system, due to many reasons I mentioned above.

After that, I talked about 3 factors that you must consider when you plan to buy yourself a new aquarium. These were the following ones:

  1. The Fish you place in the tank.
  2. The Budget you have available for the investment.
  3. The Place you have free to place the aquarium.

Think about all 3 of these aspects when you plan to buy a new fish tank. If you need to, do some thorough research to make sure you make the right decision. This is especially needed in the case of the fish you plan to put in the tank.

And lastly, I told you about some of the benefits and negative aspects that comes with owning a small and a big aquarium as well.

All in all, the choice is yours to make.

The idea is, that a bigger fish tank is better for a beginner fish keeper. You can maintain it easier, and there isn’t too much special knowledge required for that.

But if money is restraining you, a small tank is also an option. But if that is what you choose, be careful, and always keep an eye on the water quality. This way, you’ll make sure the aquarium is suitable all the time for the marine life living inside it.

Author Image Fabian
I’m Fabian, aquarium fish breeder and founder of this website. I’ve been keeping fish, since I was a kid. On this blog, I share a lot of information about the aquarium hobby and various fish species that I like. Please leave a comment if you have any question.

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