I have a Yellow-Bellied Slider. Got him initially intending to eventually put him in the pond. However, I've since decided he's an indoor-only pet for a variety of reasons.
- while YBS and RES overwinter just fine here in our city pond, I was worried about him not pulling through the winter - he was kind of expensive to risk it. I was also worried about predators getting him.
- after seeing what he does to his tank and the veggies I feed him, I don't want him anywhere near my pond plants lol. Turtles will eat just about anything. They especially love hyacinth and water lilies and will eat your pond plants.
- RES (and YBS) get pretty big and can and will damage and eat your fish.
- they are EXTREMELY dirty/messy - make koi and goldfish look tidy :sad:
If you've got a wild RES population, unless you're okay with them eating your plants and some fish, I'd probably try to discourage them from the pond area. Looking at your pond sizes, they probably wouldn't have an impact on your big pond, but might be a PITA for your small one.