Owners of red ear sliders (Trachemys scripta elegans) are often interested in housing their turtles with other animals in a mixed-species habitat. Though this is possible, and is accomplished by professionals at zoos and zoological parks, mixed-species turtle tanks are very difficult to maintain and ill-advised for most hobbyists. Red ear sliders are voracious animals and will prey upon smaller animals that are housed with them. By and large, other turtles are the best cage mates for red ear sliders, and even turtles sometimes cause problems.
Regardless of the species being considered, three strategies will aid your efforts when setting out to keep multiple species in the same tank: provide extra space, provide plentiful hiding spots and visual barriers, and ensure that all captives are very well fed. Always use a very large habitat when keeping multiple animals together, irrespective of the species involved. Whereas a single red ear slider may thrive in a 55- or 75-gallon habitat, two turtles should have at least 100 gallons of space, and 200 would be preferable. The extra space keeps the animals from being forced into constant contact, which can cause stress. Additionally, it's important to break up the cage with various hiding spots and visual barriers so a submissive animal can escape a dominant one.
Basking turtles like painted turtles (Chrysemys picta ssp.), cooters (Pseudemys sp.) and sliders (Trachemys sp.) often get along well with red ear sliders if they are the same size. In fact, different species are sometimes seen stacked atop one another basking on rocks in the wild. However, large red ear sliders will often eat or harass smaller turtles, and may sometimes fight with turtles that they simply don’t get along with; individual personalities can have a strong effect. Musk turtles (Sternotherus odoratus) are sometimes compatible with red ear sliders, but this varies from individual to individual. Additionally, if musk turtles -- who have much different habitat requirements than basking turtles -- are kept, the habitat must meet their needs as well, by offering a large, shallow section of water.
Red ear sliders will try to eat most fish kept with them. In a large habitat, fish like koi may survive with red ear sliders, though the turtles may nip their fins. Very small, agile fish like guppies may be able to survive with turtles, though they may overpopulate the tank. Goldfish and minnows are often kept with turtles because of their low cost; if they are eaten, they can easily and affordably be replaced.
Most invertebrates that are kept with red ear slider are subject to predation. It's possible to keep populations of crayfish, snails or clams with red ear sliders, provided that you understand that many of them will be eaten. By including plentiful hiding spaces in the form of submerged rocks and crevices, and using large individuals, invertebrate mortality will be limited.
Snapping turtles (Chelydra serpentina) and soft-shelled turtles (Apalone sp.) are often very aggressive to similarly sized turtles, and will simply consume turtles that are small enough to eat. Alligator snapping (Macrochelys temminckii) turtles are known to eat turtles as well, and should not be kept with red ear sliders.
Some zoos keep very large red ear sliders with small crocodilians. Some crocodilians, especially American alligators (Alligator mississipiensis), are known to eat turtles, but these turtles are much too large for an easy meal. Most hobbyists don't keep crocodilians as pets, but it does demonstrate that through careful consideration with regard to relative sizes, animals that normally predate on one another can be kept together problem-free.
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