Here’s Why Pet Rats Cannot Live in Fish Tanks

Heres Why Pet Rats Cannot Live in Fish Tanks
Heres Why Pet Rats Cannot Live in Fish Tanks

A pet rat needs an adequate amount of space to be comfortable in their living environment. Proper ventilation that allows airflow and easy accessibility for cleaning are the best housing environments for a pet rat. With this in mind, it may seem possible that a standard fish tank is an acceptable housing environment for a pet rat due to the enclosures it provides, but pet rats living in fish tanks are not a good idea for many reasons. 

Here’s why pet rats cannot live in fish tanks:

  • A fish tank lacks the proper space, ventilation, and spaces to allow a pet rat to live comfortably. 
  • Problems with humidity and improper sanitation of a pet rat’s waste can cause sickness. 
  • The plastic and glass may also cause health problems. 
  • The enclosed tank can lead to bacterial fermentation. 

Since most fish tanks are made from glass or plastic, a pet rat would have no way to achieve adequate exercise or climbing, in addition to a substantial amount of potential health concerns. This is not something that is readily known to new pet rat owners; therefore, this article will explore how a fish tank creates a toxic environment for a pet rat and how a rat cage is truly the best option for pet rat housing. 


What Makes Fish Tanks Unsuitable for Pet Rats?

Unlike fish, rats are mammals that need a large amount of space and optimal environmental conditions in their home to be healthy. Common fish tanks generally small to begin with and would give a rat no options for climbing or receiving fresh air from all sides of a tank. 

According to veterinarian Thomas M. Donnelly, housing units for pet rats should be made of a material that meets the following specifications:

  • Is easy to clean 
  • Is easy to deodorize
  • Is indestructible, even when rodents are chewing or digging in the corners 

Fish tanks do not provide any of these specifications; a fish tank is enclosed and solid, with the cleaning of potential rat waste being a messy prospect that would require the complete removal of the entire contents of the tank, as opposed to easy cleaning with a tray. 

There are four main problems that would come with using a fish tank for the housing of your pet rat. 


As mentioned, fish tanks are usually made of glass and plastic in some models. The problem with having a pet rat enclosed in the glass is that this is not a surface that would be optimal for their feet. 

The placement of rat bedding would likely ease the discomfort on the bottom of the tank, but the sides have nothing for pet rats to grip or climb onto. A pet rat would feel enclosed within an aquarium, which leads to an additional problem: inadequate space. 

Inadequate Space

When it comes to housing units for pet rats, the bigger the cage, the better. This is because rodents need plenty of room to exercise and explore. 

Fish tanks can range in size, yet the enclosure of all four walls would make a rat feel inhibited and unable to move around properly. Rat cages provide a rat with the ability to climb the sides of the cage, which is part of a rat’s daily process of exercise. Fish tanks are designed for enclosing water, not a pet rat. 

Additionally, if you were to add more than one pet rat to a fish tank, this will make the rats feel even more enclosed and limited in mobility. Airflow would become a major concern due to multiple rats vying for fresh air from the top of the tank. 

Improper Airflow

Rats are breathing and active mammals that need comfort and space in their cage, which also provides an adequate flow of air from all sides. 

A fish tank only has a top that opens, which means that airflow can only reach a pet rat from the top down. Not having access to free-flowing air can cause discomfort in a pet rat, which will also affect the rat’s overall mood and personality. 

Ventilation is also crucial for allowing fumes to escape from rat waste, which, when combined with high humidity levels, can cause a potentially toxic environment to your pet rat.  

Increased Humidity Due to the Presence of Waste and Warmth

Glass is much less dense than the material that makes up a wired-cage. 

Pet rats expel waste on a daily basis, which means the ammonia levels from urine and the overall warmth from body heat (especially if the tanks have more than one rat), can cause humidity levels within the tank to rise sharply. With the increase in humidity, bacteria from rat waste will begin to ferment due to the heat and could cause health problems in a pet rat. 

A fish tank would need to be cleaned multiple times a day to prevent this issue from occurring, which could be a potentially drastic measure if you have your rat housed in a large fish tank. 

Are Large Fish Tanks Suitable for a Pet Rat?

Fish tanks in excess of 20 gallons may help a pet rat feel a bit freer to roam and move around, yet fish tanks in general just aren’t a good idea for pet rats, no matter the size of the tank. The same issues with discomfort, humidity, and improper airflow would still be present in a large fish tank. With this being said, there are still people who choose to house pet rats in large tanks, which is certainly a feasible idea due to the space offered. 

A large fish tank that has a lockable, ventilated lid and proper rat bedding with toys and exercise equipment will fulfill a rat’s needs, yet the prospect of daily cleanings to prevent the possible health effects may not be worth the trouble. If you do choose to use a large fish tank for your rat’s home, a 50-gallon tank would be the best choice; certainly nothing smaller than 15 gallons. 

The Bottom Line: Pet Rats Need More Room and Ventilation Than What Fish Tanks Offer

When it comes down to it, there are many rat owners who choose to house their pets in a fish tank, yet most are also aware that more room is certainly better in this situation. 

There is a possibility that your pet rat will not pretest to the conditions within a fish tank and be perfectly content in this environment. It would require trying to mimic all of the attributes of a regular rat cage to truly give a pet rat all of the necessities that they need in a fish tank. 

Fish tanks just aren’t big enough for pet rats in most situations, and with the prospect of health concerns due to humidity and toxicity from fermenting waste residue, that alone makes a fish tank a bad idea for a rat home. A cage is much better. 


So, fish tanks are not the best-suited environments for a pet rat, even though there are some possible exceptions if the tank is very large and provides most of the comforts that a rat would get from a cage. Fish tanks can be breeding grounds for bacteria, which would require much more in the way of cleaning than what is normally done with a rat cage. 

Your pet rat is most at home in a rat cage that allows for climbing and proper ventilation. Save a fish tank as a temporary housing compartment when you are cleaning a cage.