Buying a goldfish tank that is large enough and designed to house the number of goldfish you plan to keep is the first step to raising healthy fish that thrive. The type of aquarium you choose can determine whether your goldfish flourish or just barely survive.

You want a goldfish tank that your fish can comfortably live in.

Goldfish can live for 15 to 20 years, and some have even surpassed the 20-year mark. But to ensure your goldfish reach adulthood, it’s important that you choose goldfish tank your fish will thrive in.

Remember that your goldfish will grow rapidly and will not be an inch long for very long, so you should plan on a larger aquarium to start. – Quick & Easy Goldfish Care by TFH Publications, Inc.

Then there’s the matter of design. Tanks aren’t just the traditional rectangle shape now. You can get fancy and buy a dazzling aquarium specially designed to enhance the beauty of your goldfish.

Let’s take a look at a few goldfish tank requirements, what to avoid, and how to pick the best option for your aquarium needs.

What Size Is Appropriate for a Goldfish Tank?

Get 20 gallons (75 liters) at the very minimum and only if you’re keeping one or two goldfish.

We’ll get to why in a minute, but you don’t want an aquarium smaller than that. Depending on how many goldfish you plan to keep, chances are you’ll want a tank much, much larger.

Yes, I know. Goldfish tanks are expensive. But on the flip side, your goldfish won’t have to breathe through murky water. Assuming the aquarium is properly maintained, of course. And it’s much easier to keep the water crystal clear in a large goldfish tank.

No matter which way you look at it, a small aquarium equates to much more work, frequent water changes, and stressed out goldfish.

In addition to those 20 gallons, you’ll need to add 10 gallons (40 liters) of water for each additional goldfish you buy (if they’re fancy). If you’re keeping slim-bodied goldfish (like commons, comets, or shubunkins), you’ll need even more space – 30 gallons for each additional fish. Take a look at my guide on common goldfish types.

But why all the space?

I’m sure you’ve heard of the one-inch-of-fish-per-gallon rule. But goldfish aren’t like tropical fish, so this rule just doesn’t apply.

Instead…

Buy the Biggest Tank You Can Afford

There are a number of reasons for this. Let’s look at a few.

Photo by Louis Hall

• Goldfish are very bulky. Because of their odd body shape, they need much more oxygen than slim-bodied, more streamlined fish of the same length. Yes, the one-inch rule might work while your goldfish are young. But as your goldfish grow (and grow quickly), so does their body. Before you know it, your goldfish are quadruple the weight they were previously. And because they’re so heavy, they’ll need even more oxygen. If your tank doesn’t have a lot of space with a wide surface area, you may find your goldfish gasping for breath near the water line. Goldfish bowls are especially harmful because bowls usually have a very tiny surface area with no room for a filtration system.
• A large tank gives your goldfish plenty of room to grow to their full potential. In a small 5-gallon aquarium, your goldfish will still grow. But growth will become stunted, and your goldfish won’t be able to develop properly. In such an environment, goldfish usually don’t last any more than a couple of years. Sadly, many goldfish never live long enough to even grow the 8 inches, 10 inches, or even 20 inches long their body was destined to be.
• Water changes can be very stressful in a small goldfish tank. Goldfish prefer water that maintains a constant temperature. A small aquarium just can’t hold enough water mass. The water will take on whatever temperature the room is, heating up or cooling down much faster than a larger goldfish tank with more water mass (more water allows for slower temperature changes). If someone happens to leave the window open or the power fails and cold air flows into the room, the quick temperature change will cause your goldfish serious stress. And if you’re doing a routine water change (small tanks require more frequent changes), your goldfish can go into shock if you aren’t careful to keep the newly added water the same temperature as the tank.
• Goldfish excrete tons of waste. More waste than most other fish species because of their heavy bodies. So every day that you let your goldfish tank sit, the water quality is getting worse and worse. When you change the water, you’re bringing the water quality back up to its original state. Because larger goldfish tanks have more water mass, the quality of the water decreases slower. Wastes are less concentrated. That’s why you won’t have to do as many routine water changes (or take out more water per change) to keep conditions healthy in a large aquarium. With a 5-gallon tank, you’ll probably have to change the water every day, taking out half of the water per change depending on how many goldfish you have (and how poor water quality is). If you’re late to change the water for whatever reason, your goldfish can quickly become sick.
• The bigger the tank, the less crowded it will be. Overcrowded tanks can cause serious health issues. Water quality worsens at a much faster rate as more waste dissolves and the water becomes more concentrated with harmful toxins. Fish also get more aggressive when they’re overcrowded. So not only are your goldfish stressed out from the poor water quality, but they’re now faced with aggressive tank mates. If they don’t suffer from a few bloody scrapes or torn fins first, a fungal infection is bound to rear its ugly head later.
• Your goldfish tank will fall short. We all have an idea of how we envision our goldfish tank to look like once everything is all set up and running properly. Some fish hobbyists might want to go all out, landscaping the aquarium with all sorts of live plants, pieces of driftwood, and gorgeous waterfall ornaments. Others might want a more simplistic look – a few plastic plants and maybe a treasure cave in the center with holes for hiding. Whatever you envision your goldfish tank to look like, chances are that you won’t be able to achieve the same look with a small aquarium. You’ll want to go much larger, and for some, this may even exceed the 20-gallon requirement.
• You’ll probably want to keep more than one goldfish. Two goldfish can’t thrive in a tank less than 20 gallons. And depending on the type of goldfish you’re keeping, you may need even more space than that. Besides, goldfish are social creatures and prefer the company. So consider how many goldfish (and which goldfish types) you want to keep before buying your goldfish tank.

Even with a large aquarium, you still don’t want to max your tank to capacity. Your goldfish will be a lot happier with a few gallons of extra space. So if you plan to keep four fancy goldfish, you might want to buy a 50-gallon tank, instead of a 40-gallon. Or even a 46-gallon bowfront aquarium.

Buy the biggest tank you can afford. You’ll be happy that you did.

Long or Wide?

Aquariums come in many different shapes and dimensions.

Photo by Ajari (Flickr)

The shape you choose should be carefully considered, since not all of them offer your goldfish the same benefits. Avoid equilateral hexagons, pentagons, and cylinders. These aquariums are usually too deep, and they don’t have a wide surface area like rectangle or bowfront aquariums.

Stay away from long, deep tanks. Goldfish are oxygen hogs and need the extra surface area in wide, horizontal setups. A wide surface area (the space at the top of the aquarium where water meets air) is crucial to keep oxygen levels up and carbon dioxide out. Long aquariums are also harder to work with, since you’ll have to reach far to move around ornaments or plants.

Besides, goldfish are much happier swimming across distances than they are swimming deep.

Acrylic or Glass?

Whether you buy an acrylic or glass aquarium is up to you. Both options have their benefits and disadvantages. Neither one is perfect.

Let’s compare the two.

Acrylic

• Acrylic aquariums are lightweight. In fact, if you take both a glass and acrylic aquarium of the same size and shape, the acrylic tank will be noticeably lighter. That’s because acrylic material is less than half the weight of glass. So you can move much larger acrylic tanks with less effort (and the floor and aquarium stand can more easily handle the weight).
• Acrylic aquariums are very durable. You don’t have to worry about major leaks from cracks or breaks. If there is some sort of collision (your kids are playing ball near the goldfish tank), the aquarium will just bend a little, depending on the force of impact. And since acrylic tanks are bonded rather than seamed together, they hold up better over the long term.
• Acrylic aquariums retain more heat. As you know, fluctuating water temperatures will stress out your goldfish. So by retaining more heat, the tank is able to keep the water temperature more constant.
• The sides of acrylic aquariums are spotless. They don’t have seams or silicone filled corners like glass tanks do (not only can seams take away from the visual appeal, but your goldfish tank can also leak if a seam gets damaged).
• Acrylic aquariums offer a clear, realistic view. The view isn’t as distorted as it is with glass. There’s also no green tint in acrylic material, as there is in some glass aquariums.
• Acrylic aquariums have more design options. You don’t have to stick with a plain rectangle-shaped tank. Enhance the beauty of your goldfish tank with a flat back hexagon or bowfront aquarium.
• Acrylic aquariums can scratch if you’re not too careful. But scratches can also be easily removed. A scratch is also much better than a crack (and potential leak).
• Acrylic aquariums can be a bit pricey. Often, you’ll find the same sized glass aquarium at a cheaper price.

Glass

• Glass doesn’t scratch. But it can break. And then you’re faced with a massive leak.
• Glass aquariums can hold their shape, even if unsupported. If you don’t support the whole acrylic aquarium on a stand, the material can bend over time.
• Glass aquariums maintain the same clarity for years. If you buy an acrylic aquarium made without UV stabilizers, it can yellow or cloud as it ages. Always check to make sure the brand you buy uses this technology before going acrylic.
• Glass aquariums are heavy. Many people recommend acrylic for goldfish tanks larger than 300 gallons, because by that point, glass just becomes too ridiculously heavy to lift (and you’ll need special equipment to even carry the empty aquarium past your front door). The extra weight is also a strain on your aquarium stand and floor.
• Glass aquariums have seams on the corners. Seams can often be damaged while scraping algae off the sides of the aquarium. And if a seam does get damaged, you may have a serious leak on your hands.
• While still clear, glass can have a green tint. This is from the iron in the glass. The more iron the glass has, the greener the tint. And so thicker glass aquariums usually have a greener tint than thinner ones.
• Glass design options are limited. You’ll usually only find glass aquariums in the traditional rectangle shape. But since these aquariums are rectangular, surface area is maximized to provide your fish with better aerated water.

The goldfish tank you choose is up to you. Either an acrylic or glass aquarium will do. But remember: Always buy the biggest aquarium you can afford. Make sure it’s wide (from left to right) and not long (top to bottom). Goldfish need the space to thrive. The more surface area your aquarium has, the better aerated the water will be.

Which Goldfish Tank Do You Prefer?

Do you buy glass or acrylic? What sized aquarium do you have? How many goldfish do you keep? Share your thoughts in the comments below!

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