Can red eared sliders be in the same tank with other turtles?

Yes they can as long as you follow the rule about 10 gallons per inch of shell for all turtles. For instance= 2 2 inch turtles need 40 gallons not just 20. Make sure the turtles are near the same size and you don't have two males or there will be aggression. Also, if you have a male and a female prepare for them to mate. Also, the tank gets dirtier a lot faster.