In short, yes you can have turtles and fish in the same tank. This is not a one size fits all answer though, as it depends on the species as to whether they can live in harmony.
As with mixing any animals, there is always a risk that they will fight and some may become injured or sadly pass away. It is important to be aware of the possibility of this before attempting to combine species.
Turtles are omnivorous animals, meaning that they will eat both meat and vegetables in their diet. If you are planning on introducing fish into your turtle tank at any point, we recommend not feeding them feeder fish before. If they learn that fish are food, then they will try to eat your pricier fish too.
It is not recommended for beginners to attempt to combine different species. There is a lot of knowledge needed to ensure the safety of all the animals and keep them thriving in a shared environment.
The Type of Turtle
The type of turtle you get dictates how good of a predator they are. Some types of turtles are very efficient at hunting and consuming fish. These turtles are unlikely to be a good tank mate with fish.
Red-eared slider turtles, painted turtles, and cooters are very strong hunters. Mud turtles and musk turtles are much weaker hunters and have little interest in it. This makes these species much more suitable for cohabitation. Snapping turtles should not be mixed with any other animals.
The age of the turtle is also important. The older the turtles get, the less protein is required in their diet. This means that older turtles are much more likely to be vegetarians and only eat plant foods. Olde turtles are very unlikely to eat fish as a food source.
The Type of Fish
Like with people, some types of fish simply will not adapt well to living with others. It is vital to consider the species of fish you wish to reside with your turtle.
The fish you choose should be able to move very quickly. They should be able to easily evade capture by the more slow-moving and clumsy turtle. Being small or thin also helps with this. It is not wise to put long-finned fish in the same tank as turtles. This is because they can easily get caught in the turtle’s jaws.
The fish species you purchase must be relatively smart in fish terms. They must be able to understand that they must avoid capture by the turtle. They must be spatially aware enough to know to move out of the turtle’s path to stay alive.
You do not need to be concerned if your fish appears a little aggressive. This can work to their advantage. If your turtle approaches them and they snap back, it could dissuade your turtle from eating them. However, if the fish is too aggressive then they could potentially hurt or kill your turtle.
Never house your turtle in the same tank as a catfish, a piranha, a lobster, or an electric eel. You should also avoid combining guppies or goldfish with turtles. This is because they produce a very large amount of waste which could pollute the water for the turtles, plus they are very small and likely to be eaten.
Zebrafish, Tetra fish, plecos, and yellow cichlids tend to respond well to cohabitation with turtles. You should only ever introduce a few yellow cichlids to the tank. This is because they are larger than the other fish and very territorial.
If they are mating and the turtle interrupts, they have a tendency to become very aggressive and could injure your turtle.
It is not a good idea to keep invertebrates in the same tank as turtles. They are incredibly likely to get eaten by the turtle, even if there are decent hiding places.
It is not fair to the invertebrates to put them through this. Some larger apple snails are likely to be okay in the tank with a turtle, however, smaller ones may be eaten. These have the added bonus of keeping the tank clean as they feed on algae.
Shrimps and other crustaceans are suitable for keeping in the tank with a turtle. However, turtles see shrimp as convenient little snacks and you should always keep a variety of hiding places in the tank for them.
It is likely that soft shell crustaceans will eventually be eaten by your turtle, so bear this in mind. Ghost shrimps tend to survive well in the same environment as a turtle.
Different species of turtles are likely to compete with each other. This can just be little spats, but they have also been known to maim and kill one another. Larger turtles are likely to intimidate and injure smaller turtles, even if they are from the same species.
If your tank is home to 3 or more turtles, and one is female, the males are likely to fight over her.
The Size of the Tank
As a general estimate for tank sizes, you should allow a minimum of 10 gallons of water per inch of shell length. You should look at the general size your breed of turtle grows to be, and use this as the way to work out the space requirement.
At an absolute minimum, you will require a 40 or 50-gallon tank. This is because it is illegal to sell turtles less than 4 inches long in the United States. Be warned, that if you start out with a tank this small it will need replacing as your turtle grows.
The depth of the tank is also important. At a minimum, this should be 2x the shell length of your turtle.
We recommend a minimum tank capacity of 80 gallons if you are looking for turtles and fish to cohabitate. Less tank space means that the fish and the turtles are more likely to fight with each other.
How to work out the number of gallons your tank holds
You will need to measure the interior dimensions of your tank. You need the width, length, and height of the water. You should measure this in inches.
Multiply these 3 dimensions by one another. For instance, if the water takes up 26 x 40 inches inside the tank, at a depth of 18 inches, the total volume will be 18,720 cubic inches.
There are 231 cubic inches of liquid per gallon. To work out the volume of your tank in gallons, you need to divide your original sum by 231. In this case, it would be 18,720 / 231 to give an answer of 81.03 gallons. A tank with these dimensions would allow your animals 80 gallons of water to live in and explore.
Setup of the Tank
We suggest placing some ornaments and hideout caves inside the tank with your animals. These will allow the fish to hide from the turtle, meaning that if they feel threatened they have a safe space to retreat to.
Some good and cheap ideas for hiding places include PVC piping and inverted flower pots. Synthetic water plants are also good hiding places for smaller fish. You should use synthetic rather than real as turtles will eat away natural vegetation, removing the hiding place.
Turtles need a lot of additional support and machinery inside the tank to keep them at optimal health. These include UV basking lamps, which some fish may not respond well to.
The filtration system inside a turtle tank must be powerful. This is because they release a lot of waste into the water as well as anything they nibble on floating freely.
We recommend a canister filter, as this utilizes chemical, biological, and mechanical filters to appropriately filter the water inside the tank. They also mount under the tank to prevent taking up space inside the water.
If you are planning on introducing fish to the tank, it is even more vital to have a sufficient filter for the water. Turtles are much hardier animals and can cope with less clean water, but this is not the case with fish.
You will also need to keep a closer eye on the pH of the tank, ensuring at least once a month that the level remains between 6 and 9. The optimal water pH for turtles is between 7.4 and 7.8. Freshwater fish need a pH of 5.5 to 7.5 and saltwater fish need a pH of above 8.0.
The ammonia and chlorine levels should be as close to 0 as possible. You will also need to aerate your water to ensure there is sufficient oxygen to sustain life.
Some fish, such as goldfish, need cold water to thrive. Anything above 74 degrees Fahrenheit is likely to be too warm for them. This temperature is simply too cold for most turtles. This is one of the reasons why it is not recommended that you house goldfish and turtles together.
The optimal temperature for turtles to live in is somewhere between 75 and 86 degrees Fahrenheit. You should look for tropical fish that also reside in this water temperature to make the best tankmates.
How to Introduce Fish Into a Turtle Tank
To begin with, you need to ensure that your tank is sufficiently large. We suggest feeding the turtle before introducing any new fish. If it is full, it is less likely that it will chase the fish around the tank.
We suggest introducing fish when your turtle has matured. By this time they will be much less likely to eat other animals, focusing their diet mainly on plants. This will also give you a better judge of the size discrepancies between the species.
Your fish is likely to come in a bag of water, which is unlikely to be at the same temperature as your tank. The first step is to float the bag containing the fish on the surface of the water in the tank for 5 to 10 minutes. This will allow the bag’s temperature to slowly drop or rise to the same as the water in the tank.
Every 5 minutes, gradually add more water to the bag from the tank. Repeat this process until the volume of water in the fish bag has doubled. This means that your fish is ready to be released into the tank.
Keep an eye on your turtle’s behavior when the fish is first introduced. If the turtle begins to lunge at the fish or snap at their fins or tail, you should immediately take the fish out of the tank. It will need to be housed separately from the turtle as this is a clear indication that the two do not get along.
Can multiple turtles live together?
Generally speaking, the answer is yes but with a few caveats. The turtles must be of the same species and should be of a similar age. You should not house adult and juvenile turtles together. This is because the younger turtles will be smaller and the larger ones may see them as prey.
There are some species of turtles such as snapping turtles and softshell turtles which are very territorial. These species are too aggressive to be housed with more than one to a tank and must live alone.
You should be aware that male turtles are likely to snap at one another in a display of dominance.
If you want to place multiple turtles in the same tank you must ensure it is of a sufficient volume. Larger spaces will reduce the levels of tension and aggression between the turtles.
You should also ensure there are many hiding places in the tank so that they can have one each. The basking platform under the UV light must be large enough to allow them all to bask at the same time.
Can turtles live with tropical fish?
This is not really recommended. Tropical fish usually have long fins and tails which attract a lot of attention.
There is a large risk that the turtle will view these fish as food. They are likely to snap at the fins which could cause injuries or death.
It is also a lot harder for tropical fish to hide in the cage due to the floaty fins, again putting them at an increased risk of danger.
Can turtles live with goldfish?
Aside from the temperature issue mentioned above, there are other reasons why turtles cannot live with goldfish.
Goldfish produce a large quantity of waste relative to their size. Primarily, they excrete ammonia. You should keep an eye on the levels of ammonia, nitrites, and the pH of the water. Having goldfish in your turtle tank will throw all of these levels off and could cause harm to your turtle.
Goldfish can also grow to become very long in some cases. The size of a goldfish can easily overtake the size of your turtle. They are also very proactive breeders and could overpopulate your tank.
Can turtles live with koi fish?
These are more likely to live in harmony with turtles than other fish, but would still not be our first choice as a tankmate.
They are very small when they are babies and as such, are incredibly likely to be nothing more than a gourmet meal for your turtle. They are also very expensive, and no one wants to waste money on something that will not live longer than a few minutes.
Koi fish, like goldfish, can grow to become very large. As adults, they are easily larger than most turtles. For this reason, they need a lot of space. They tend to survive better in outdoor pond habitats than in indoor aquariums.