Last update: November 12, 2022

What Aquarium to Buy? Things You Need to Know When Choosing Your First Aquarium

Woman choosing a tank from her local fish store

It’s a fact:

If you want pet fish, you need an aquarium.

Because of this, it’s the first piece of equipment that you will buy.


There. Are. So. Many. Aquariums.

If you’ve walked into your local pet store, or shopped online, you know that aquariums come in all different sizes and shapes.

And then, there are starter kits – all-in-one aquarium solutions that promise the world and under deliver.

With so many options to choose from, how do you know which aquarium is right for you?

Wonder no more! I put together a list of 7 important factors to consider when choosing your first aquarium…

1. Bigger is better. Always.

Big fish bowl next to small fish bowl on counter top

Before we discuss what you need to consider when choosing the right-sized aquarium, there is one thing I want to make clear…

Choose the largest tank possible!

This is something that catches a lot of beginners off guard. A larger fish tank is easier to care for than a small one.


You see, your fish are going to produce waste. A lot of it. It’s unavoidable.

Waste includes:

  • Poop
  • Pee
  • Uneaten fish food

As waste breaks down, it produces chemicals that are toxic to fish. This is one of the main reasons we perform water changes – to remove these built-up chemicals from the water.

These chemicals build up quicker in a small aquarium than a large one.

Let’s use an example to make this concept easier to understand…

Say these chemicals are a teaspoon of instant coffee.

What happens if you add this coffee to a cup of water?

The water turns brown, right?

But if you add the same amount of coffee to a swimming pool, there would be no noticeable change. The large amount of water dilutes the coffee to such an extent that it is unnoticeable.

Well, the same is true of your aquarium – these chemicals quickly build up and become dangerous in smaller tanks. You will need to perform precise and regular maintenance, which can be a big ask of any beginner.

A larger tank leaves room for error. And as a beginner, expect to make many. I know I did!

So, leave the small tanks, bowls and jars to the experts. As a beginner, start out with at least 15 gallons.

With that out of the way, let’s take a closer look at what to consider when choosing the ideal-sized aquarium.

2. Where are you going to put the darn thing?

Woman choosing a table as the best location to set up her glass fish tank

In a previous guide, I explained ‎how to find the perfect location for your fish tank in your home.

If this is your first aquarium, I recommend reading that guide first. That place where you are considering setting up your aquarium might not be so ideal after all. It’s important to get it right because that heavy fish tank is going to be a huge pain to move once it is set up and filled with water!

But back to the point…

The location impacts which fish tank is right for you.

For example, a gigantic fish tank might need a stand to support its weight, which is going to take up more space in your home!

3. How much can you afford?

Hand with money inside fish tank

Next up, you have your budget.

I’ll level with you, the bigger your aquarium, the more expensive it is to maintain.

This has to do with the amount of water the aquarium holds.

The more water your tank has…

  • The larger the heater
  • The bigger the filter
  • The more water conditioner to treat the water

…You get the idea. These all add to the cost of the aquarium.

Now like I originally stated, when it comes to aquariums, bigger is certainly better. But if you are on a tight budget, you may have to compromise on the size of your aquarium.

4. The size and type of your fish

Fish squished into aquarium that is too small

It can be easy to forget, but fish grow.

The majority of fish sold at your local pet store are babies. With care from you, these fish will grow until they reach adult size. The bad news is that the adult size may be larger than your aquarium can accommodate.

Take a goldfish for instance. I am sure you have seen them comfortably fit into a small glass bowl. Guess what? An adult goldfish can grow larger than 12 inches! That bowl is not going to comfortably hold it for long.

If your fish grows too large for your aquarium, then you have two options…

1. The expensive option: Buy a larger fish tank

2. The cheaper, sadder option: Say goodbye to your beloved fish

Buying the right-sized tank in the beginning ensures that you don’t have to make this difficult choice.

However, just because a fish is small doesn’t necessarily mean it is right for your aquarium. Some fish are very territorial and will bully any fish that ventures into its area of the tank.

So, when deciding which fish you want to stock in your tank, research is key. You want to consider the adult size of the fish as well as their temperament – your tank needs enough room for the largest and angriest fish you want to stock.

5. How big is the opening of the tank?

Most beginner’s guides don’t even mention this point. Most likely because it is difficult to explain. But because it’s so darn important, I simply had to include it in this guide.

You see, fish breathe oxygen. Just like you. Just like me.

If you put more fish in an aquarium than there is oxygen, they will suffocate.

That’s easy enough to understand, right?

How the oxygen enters the tank is through the surface of the water.

The larger the surface of the water, the more oxygen that can enter the aquarium. And, the more oxygen that is available, the more fish that can live inside without suffocating.

In fact, it is often not the size of the tank that limits how many fish you can keep but the surface area of the water.

Consider the following two tanks…

Besides the height, both are the same size.

Different sized fish tanks diagram

Now, any newcomer is going to assume that Tank B will hold more fish.

But if you look at these tanks from above, you notice that the opening and surface water area are identical…

Surface area of two aquarium tanks diagram

And because of this, both tanks will hold the same amount of fish.

While there are some ways to cheat and add slightly more oxygen, like using an airstone to aerate your aquarium, the opening of your fish tank is going to be the biggest limitation to how many fish you can stock.

So, if you are choosing between two similar aquariums, choose the one that allows for a larger area of surface water.

6. Glass or acrylic?

I get asked this question a lot, fortunately it’s one with a simple answer…

For any tank under 150 gallons, a glass tank is recommended. And between you and me, I don’t think there are going to be too many beginners buying a tank larger than that.

Why do I recommend glass?

I explain it in more detail in this guide, but basically, acrylic tanks scratch waaaaaay too easily. Even the pebbles you place at the bottom of your tank can ding it up.

While acrylic is easily repaired, do you really want the extra hassle of buffing out scratches?


And besides, in this size, glass tanks are cheaper and much easier to come by.

Glass all the way!

7. Avoid the kits

Aquarium starter kit with equipment

They are everywhere!

Aquarium kits, I mean.

These kits claim to provide every piece of equipment in a single box that you need to set up your fish tank.

Also known as starter kits, these all-in-one aquariums are a trap that I see beginners fall for time and time again.

And, that is often not helped by a pushy salesman who doesn’t have your best interests at heart!

An aquarium kit often includes:

All for one low price! Sounds appealing, right?

Unfortunately, 99.9% of the time, these kits suck. Like, really suck. And that’s putting it nicely!

Not only are the aquariums often too small, but the extra equipment is junk.

Clip-on lights that fail after a week, inaccurate thermometers, filters that do anything but…

To put it simply, starter kits are cheap and nasty.

Let me stress this:

You are trusting this equipment with your fish’s life!!

If it fails – your fish will die.

So yeah, it’s not exactly something you want to cheap out on.

Do yourself a favor and buy reliable, quality equipment – your fish will thank you when it’s still working years from now.


If you made it this far, you now have all the information to choose the perfect fish tank for you.

Just remember to take your time when choosing. Once set up and filled with water, a fish tank cannot be easily swapped out for a new one.

Got a hot tip on buying a new aquarium? Let me know in the comments below!

Ian Sterling

Ian Sterling, founder of, began his aquarium journey over 30 years ago, driven by a deep fascination for fish and their diverse personalities. His website,, is dedicated to making fishkeeping accessible and enjoyable, offering beginner-friendly guidance, expert insights, and a community for aquarists to connect and share experiences.

Comments (9)

Thank you for your guide. Made me decide to get a larger tank. Got a good big tank at Petsmart during their dollar per gallon sale.

Hi Lars,

Happy to help. You won’t regret your decision – not only can larger tanks hold more fish, but they give you more choices when it comes to decorarting them!

It’s good to know that glass tanks don’t scratch like acrylic tanks do. This is helpful since I’m looking into getting an aquarium in the near future. I’ll stick to looking at glass for this reason.

Thank you, Ian, for this cool explanation. You literally opened my eyes. Unfortunately, I can’t figure out which kind of gallons you meant here (British or American). It’s important because this system is not common in my country. We use liters and there is a huge difference between these quantities of water. So could you specify this? Thanks for your amazing article again!

Hi Slava,

When I first wrote this, I didn’t imagine anyone would read it, much less people from the other side of the world. I’m American, born and raised. Everything you see on this site references American gallons. If you need any more help, just leave a comment. Welcome to the hobby!

Hi, Glad to find your post. You mentioned that kits should be avoided. I’m a newbie at fish keeping and was wondering if you have any guidance on selecting reliable and quality equipment.

Hi Denise,

It entirely depends on where you are, what you plan to stock and your budget. I highly recommend chatting to your local fish store (avoid big chains, like petco) as they will be using the same or similar water to you and best advise on what your particular tank needs – they are a wealth of knowlege for those of you starting out.

Hi Ian,

This is a very interesting post and very helpful for novices like me. Getting an aquarium has been on my wish-list for quite sometime now, but I had to hold off on that as my kids were too young. Now that my youngest is 3, she has a greater appreciation of all things dangerous (electrical sockets, glass et al) and all things living.
Couple of questions:
1. Does having an aquarium work for a family that occasionally travels for a week. Unlike our four legged friends, whom we can take along, I dont see myself carrying a fish tank around ;). It might sound like a dumb question, but do oblige. Is there an auto-feeder option?

2. I read somewhere that for beginners like yours truly, it is recommended to go for Freshwater rather than saltwater due to maintenance challenges. Your thoughts?



Hi Brigu,

Excellent questions. Occasional weekly travel isn’t much of a barrier to owning fish – we all need a vacation right? There certainly is automatic feeders and other ways around this problem. Here is some additional reading on these two topics:

As for your second question, I would agree that for a beginner, freshwater tanks are easier. There are extra steps to a salt water tank such as mixing up salt each water change and monitoring the salinity. And certain types of fish and anemones require a very delicate touch. It’s not that you couldn’t overcome these obstacles, but when you are already learning how to cycle a tank and the rest of the information that comes from being a beginner, it may be too much to take on at once. I would also add that there more freshwater fish keepers around, which makes it easier to find advice on what to do with a fresh water tank – for a beginner, that support can be very helpful.

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