No. Keep the temperature at 25 C.
He is probably trying to hibernate
Yes Red ear slider turtles hibernate. If you have a lamp though it might not because it doesn't know when it's cold. So if you want it to hibernate then turn off it's lamp in the winter, so it can experience what it's like to be asleep for a whole season.
First of all it's called Red-EARED slider. Secondly if you keep it home he shouldn't hibernate. Unless you really need it, then you have to keep the water always clean and provide the turtle with enough food. Red-Eared Slider should go into hibernation state when the temperature of air drops below 10 degrees. But still I advice you to keep him out of getting into hibernation.
they dont hibernate they brumate. In the wild they start brumating in October when the temperature reaches below 10 °C (50 °F) and they come back up in March. In captivity they cant brumate at room temperature.
You can keep your slider in a small outdoor pond stocked with small live feeder fish, small snails, and aquatic plants. You can also keep him in an 75 gallon plus indoor tank. You should always bring your turtle in for the winter to keep him from hibernating or from freezing to death.
Red-eared slider turtles usually can only breed successfully if they have hibernated before, and turtles kept in tanks rarely hibernate. There is a miniscual chance your turtles will breed if they have not hibernated.
Red-eared sliders are one of the most common types of turtles found in the pet trade, but ... are good for young turtles, but as red eared sliders mature ... more like indoor ... yes they are good indoor pets
Carrots
They can be housed outside, yes. Just make sure they have everything they would get from an indoor enclosure.
Yes you can they just need barrier that goes in the ground where they can't dig out and escape. They also need a land area where they can hibernate in the winter.
feed raw chicken or meat due to the risk of bacterial contamination. Also See. How Much Should I Feed My Red Eared Slider? How Should I Give My Red Eared Slider Its Food?
Gregory