Reptile tanks (or vivariums, as they’re technically known) are usually built rather differently from fish tanks and shouldn’t be filled with water.
Occasionally, however, you can find a vivarium that is designed to be dual-purpose and can double as an aquarium.
But how do you know if your vivarium can be used as a fish tank, and how would you go about converting it? All of the details are coming right up.
The Different Types of Tank
Before we begin, it might be wise to clarify terms, as well as introduce you to some types of tanks you might not be familiar with. Understanding the etymology (the origins of the words) can be helpful here.
The word ‘arium’ comes from Latin, meaning a container or receptacle. So aquarium literally means a receptacle containing aqua – or water! But what other kinds of ‘ariums’ are there?
- ‘Terra’ (Earth) + Arium (Container) = Earth Container
The word terrarium is often misused to mean a tank that houses reptiles and amphibians, but it more specifically denotes a tank solely for soil, plants, and other ornamental items such as moss, pieces of wood, or decorative rocks.
- Vive (Living) + Arium (Container) = Living Container
Vivarium is the proper term for dry tanks that host any type of reptile or other pets that never need to be submerged in water.
- Palus (Swamp, Marsh) + Arium (Container) = Swamp Container
A type of tank that even my spellchecker doesn’t recognize is the paludarium! It features dry land and water in similar proportions.
Paludariums are excellent for frog and turtle species who enjoy spending some of their time on land, and some of their time in the water.
- Ripa (Coast, River Bank) + Arium (Container) = Coastal Container
Ripariums are a bit like paludariums, except they have much less dry land. As the name suggests, they’re designed to create a coastline, with just a small proportion of dry land for animals to take a break from the water.
How Is a Vivarium Different From an Aquarium?
A purpose-made vivarium is simply made to house dry land reptiles and is built quite differently from aquariums, paludariums, or ripariums that are designed to hold water.
For a start, vivariums don’t need to be waterproof. Whereas aquariums have watertight seals that are made from highly durable pure silicone, vivariums can be sealed with other materials such as acrylic glaze, which won’t hold water in the long run.
Different Glass Thickness
Secondly, since they don’t hold water, vivariums don’t need to be nearly as strong as aquariums so are made with much thinner glass.
Whereas a typical 55-gallon aquarium would have quarter-inch (6mm) thick glass, a typical vivarium of the same capacity might only have eighth-inch (3mm) thick glass panels.
Of course, this also makes vivariums only around half the weight of a typical aquarium!
Vivariums often have doors that slide or swing open on the front to provide easy access to feeding and handling your pet.
Obviously, these types of doors aren’t watertight, so this style of vivarium is unsuitable for containing even small quantities of water.
Aquarium lids tend to be tightly sealed to maintain a humid atmosphere above the water and minimize evaporation and loss of heat.
Vivarium lids, on the other hand, are often made with good ventilation in mind, and may simply consist of a mesh or a plastic lid with lots of openings. Both are unsuitable for housing water.
Why Most Vivariums Are Unsuitable To Hold Water
As you’ll probably have realized from the above list, vivariums are specifically designed for dry environments and are unsuitable to be turned into aquariums, or even hold smaller quantities of water for paludariums or ripariums.
The different types of glass sealing and different thicknesses of glass mean attempting to fill them with water will likely lead to leaks or even cracks in the glass. This is not only unsafe for your pets, but also for you and whatever you don’t want to get wet under your tank!
Occasionally, however, manufacturers might advertise tanks as being suitable for both reptiles and fish, so it’s still possible that some types of vivariums could be used as fish tanks.
How To Know if Your Vivarium Can Be Used as an Aquarium
Since there’s a small chance that your vivarium can also be used for fish, you need to know how to identify it.
If you still have the box that the tank came in, the description should tell you. Normally manufacturers will also leave a sticker on the bottom of the tank to specify its intended uses.
If you don’t have the original box or sticker on the bottom of the tank, you can measure the thickness of your glass to see if it’s thick enough to handle water pressure.
As mentioned, 55-gallon aquariums will usually have quarter-inch glass, whereas purpose-made vivarium glass for that size would be around one-eighth inch.
If the glass seems thick enough, next check the seals. If the tank is sealed with thick, 100% silicone sealant, it should, in theory, be able to hold water. If you’re willing to take the risk, you could try filling it with fresh water and checking whether it’s watertight.
Turning an Old Reptile Tank Into an Aquarium
If you’re 100% sure that your old vivarium was also intended to hold water, you could go ahead and try turning it into an aquarium. But before you do, please understand the dangers involved in turning an old reptile tank into a fish tank.
If the glass breaks it could cause damage to your home, your pets, and yourself. If you decide to give it a try, you do so at your own risk.
Reptile tanks contain a completely different ecosystem from aquariums, and the biochemicals and microorganisms present may be harmful to your fish. Skinks and some amphibians in particular can give off secretions that are toxic to aquatic pets.
Therefore, to convert a reptile tank into a fish tank, you need to do a lot of scrubbing! Use natural, biodegradable cleaners such as vinegar and baking soda to thoroughly clean every corner of the tank.
If you use bleach, be sure to use a de-chlorinating agent afterward to neutralize the toxic chemicals, and never, ever, use soap for cleaning fish tanks, since even tiny amounts can be deadly to them.
Rinse thoroughly before proceeding to the next steps.
If your lizard tank had a lid with holes in it, replace it with a proper, tightly sealed aquarium hood to minimize water evaporation and heat loss.
Also, make sure that whatever your tank is standing on is strong enough to withstand the enormous extra weight it will gain when filled with water! You can use our handy tank weight calculator to figure out how much that will come to here!
Other than that, once your tank is clean, you can use it like a secondhand aquarium.
Simply fill the tank with substrate, rocks, decorations, live plants, a decent heater, and a reliable filter, and let the tank cycle for a month or so.
Always test your water thoroughly before adding your first fish. Consider adding fish that aren’t too expensive or precious to you, to begin with, just to make sure everything is as it should be!
Can I Keep Turtles in a Vivarium?
Pet turtles such as red-eared sliders and box turtles need tanks with water and land to remain happy. Technically, then, their tanks should be referred to as paludariums or ripariums, depending on how much water they contain.
Just like aquariums, a tank must be purpose-built with silicone sealant and thick glass to withstand even small amounts of water. If you can’t be sure that your tank was designed to hold water, don’t take the risk!
Can I Keep Reptiles in a Fish Tank?
Normally, yes! Although you can’t usually keep fish in reptile tanks, you can almost always keep pet reptiles in old fish tanks.
With some minor adaptations, like changing the hood to a well-ventilated lid or mesh, you could keep all kinds of snakes, skinks, lizards, and chameleons in an ex-aquarium.
The only exception would be for pets that require special handling, where doors that open on the front of the tank could be highly advantageous!
Reptile tanks or vivariums are usually unsuitable for use as fish tanks. But you may be lucky and find one that was designed as dual-purpose that can also host fish.
With a little bit of elbow grease and refurbishment, it’s possible that your old reptile tank could become a sparkling aquarium, and old aquariums can nearly always make perfectly good reptile tanks.