Can a Reptile Tank Be Used for Fish?

Whether you’re an experienced fish owner or a first-timer, one of the most essential parts of preparing to bring home new fish is finding the right tank.

Multiple components will influence your purchase, such as size, shape, and the type of fish you’ll be putting in it.

With all the tank choices out there, sometimes it can be easier to grab a reptile tank instead, which to the naked eye, seems to have many things in common with regular fish tanks.

So is it safe and smart to use a reptile tank to house your fish?

Today, we’re answering that question and learning about the reasoning behind the answer.

The Short Answer

When it comes down to it, reptile tanks should NOT be used as replacements for fish tanks

Housing your fish in a reptile tank instead of a fish tank can actually result in accidents and be dangerous for your fish.

The Main Differences Between Fish and Reptile Tanks

While a fish tank is considered to be an aquarium, reptile tanks are referred to as terrariums

Although they look very similar to an untrained eye or upon a quick first glance, each is made with different materials and designed for different purposes.

What They’re Designed for and Made With

Obviously, fish tanks are designed to hold fish, and reptile tanks are designed for reptiles.

But on a deeper level, aquariums are made for the purpose of holding water, while terrariums are made for dry use to house both reptiles and plants.

It’s all right there in the names, actually. The Latin root “aqua” means water, while the corresponding Latin root “terra” means land.

So an aquarium is a tank for water, and a terrarium is a tank for land.

Why is this an important distinction, you might ask? They both are generally the same shape, are made with clear glass, and are used to house small pets. 

Well, the design of both these types of tanks informs the materials they are made with and the techniques used to make them.

Thickness of the Glass

The most important difference between an aquarium and a terrarium is the thickness of the glass they’re made with.

Terrariums will always be made of thinner glass, while aquariums have thicker glass walls.

This might seem like an inconsequential detail at first, or maybe even a discrepancy between different manufacturers.

But it is indeed a conscious choice you’ll find reflected every time you compare a fish tank to a reptile tank.

The reasoning behind this makes complete sense. Thicker glass is stronger and therefore better at withstanding pressure and weight.

When you’re choosing a tank for fish, you want one that can withstand constant water pressure pushing from within and hold up under the weight.

For reptile tanks, thicker glass simply isn’t necessary because the environment doesn’t need to exist under water pressure.

So if you end up filling water in a reptile tank, there is a possibility that it’s the thin glass walls won’t be able to hold the water and it may crack or break.

Water-Tight Seals

Another component that terrariums don’t need is water-tight sealing.

Although plants, gravel, and other environmental components are used in terrariums, they’re never expected to be totally filled with water.

In some cases, a water-tight seal could create conditions that are too harsh and extreme for terrarium-dwellers.

This is one reason why reptile owners often fit the tanks after the fact with heating lamps or other climate-controlling accessories.

The climate inside the tank should be natural and not stifled by a totally watertight seal.

On the other hand, aquariums need that sort of thick, tight seal to maintain the correct water level for fish and prevent cracks, leaks, or breaks and damages to the glass.

While silicone is often the material of choice to seal both types of tanks, the silicone layer along the sides of the glass in aquariums will be much thicker but also more even, straight, and sturdy looking. 

Lids of the Tank

Another distinguishing factor between these two types of tanks is the type of accessories that often fit each of them.

Firstly, the top of each tank, and therefore the lid around its border, will also be different.

Thinking back to the primary purpose of each tank, the job the lids do corresponds to each.

For an aquarium, it’s to maintain the water level and pressure and prevent leaks. For a terrarium, it’s to provide a safe and controlled environment that’s easily cooled or heated. 

So terrariums will usually have a lid that is fitted with mesh or some other type of breathable material.

Depending on the type of terrarium, it might not have this component.

But if it doesn’t, it’s likely to have a front-facing or top-opening door through which to gain access to the inside of the tank for feeding your pet or cleaning the tank.

Obviously, aquariums will never have front-facing doors!

Instead, they’ll mostly always have glass lids that slide from the side or fit down into indentations around the top of the tank.

This further adds to the sealed environment and helps prevent any accidents that could occur from the top getting knocked off if the tank was bumped or jostled.

How to Tell if You Have a Fish or Reptile Tank

For many people who intend to browse their local pet store to purchase a tank that corresponds to the kind of pet they’ll be bringing home, knowing the differences between the two can steer them in the right direction.

However, if you’ve bought or have been given a tank secondhand, it could be a little harder to put that knowledge to work.

So let’s go over how you can inspect the tank you have and determine if it’s a fish or reptile tank.

Try the Water Test

One of the most trusty ways to tell if you have an aquarium or terrarium is to test if the seal is waterproof or not.

A small experiment could be in order if you can’t tell just by looking at the silicone seals.

Simply fill the tank with water and place it outside with the top on, out of the sun.

If the water fill level has changed drastically in just a few hours (don’t forget to check the ground around it for puddles), then you’ll know the seal is not air-tight. 

It’s important to note with this test that putting the tank somewhere you don’t mind getting wet is crucial!

Not only could the area get wet, but if the glass walls are particularly thin, depending on the amount of water you use to test it, the tank could crack and break, which could prove to be dangerous.

Try the Weight Test

If you’d like to try something a little less extreme with more instant results, then try out the weight test.

Because aquariums are made with thicker glass than terrariums, they will be much heavier than their reptile counterparts.

If you feel comfortable doing so, simply pick up the tank to test its weight.

For those who have held an aquarium or terrarium before, you’ll likely instantly be able to tell which you currently have. 

Try Something More Technical

If neither of those seems your speed, you can always resort to a more definitive test.

Measuring the thickness of the glass with a set of calipers, an instrument that measures width, will allow you to compare the glass thickness to the length of the tank.

Because the glass thickness must correspond to the size of the tank and consequently the amount of water pressure it will have to withstand, the thickness of the glass will vary based on the size of the aquarium.

However, use a chart like this one as a rough guide to how thick the glass should be for aquariums of different sizes.

If you have a tank of a certain size with thinner glass than the chart calls for, then there’s a good chance that you have a terrarium instead. 

When All Else Fails, Consult the Experts

So what do you do when all the tests have proven inconclusive, or you’re not able to try them?

There’s absolutely no harm in taking your tank down to your local pet store and asking someone who works in the fish section to take a look at it for you.

An associate familiar with fish tanks will likely know very quickly which kind you have and can either help you understand how to best set it up or direct you toward an alternative.

Final Thoughts

A good quality tank can be a great, dependable home for your fish for years to come.

However, making sure you have an aquarium tank instead of a terrarium is essential before bringing your fish home and setting up their new environment.

Although fish tanks can often be far more expensive than terrariums due to the material they’re made from, it’s best, in the long run, to use a fish tank instead of a reptile tank.

Aquariums have air-tight seals designed for keeping water-dwelling creatures happy and safe.

If you’re worried about the expense of a fish tank, consider looking for one secondhand.

Inspecting the tank before you buy and making sure that it has all these definitive aquarium qualities can save you time and money, and your fish won’t know the difference!

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