Hey good luck with this guy. I am not sure where you are located but I do feel the need to toss this out there for all future turtle owners.
I dont want to be the downer on this but also check your local laws. RES are being banned by many cities and states.
Petstores can not sell these legally as Pets at this size in the US. They typically claim to sell them for educational purposes.
These are one of the most unwanted animal in the pet trade. Humane societies and local pet control are getting more and more of these every year. Due to people no longer wanting the adults. They are messy and hard to take care of.
Heck, here in MN there are sightings of some in local ponds. they are starting to survive up here as well, they are a very invasive species.