my river cooter is trying to woo my res

Question
I have a River Cooter and a res in the same 100 gallon tank my cooter is fluttering on my RES does this mean I need to make breeding arrangements? Can they actually mate? They grew up together so it could just be because they like each other but while funny to watch I am concerned about what to do if they actually breed. I was thinking a kiddie pool with a large salad bowl in the center for soaking and sand up to rim of bowl so she can lay eggs. I love my turtles and just wanna make this as easy as possible on them. I mean if they are mating. I already have one pool for sun basking for a few nice afternoon hours on my patio with a rock in the center for getting out of the water but I could add sand.

Answer
Breeding is possible if one is male and one is female of course, and they are sexually mature. It doesn't matter that they are different genus. Aquatic turtle genera cross breed all the time.

Your Cooter would appear to be male by performing this behavior, but it does not mean you necessarily have a female RES. He might be confused, and that happens too sometimes when there are of two different genera, or in cases where there are not enough available females around.  

It is unlikely that this behavior is happening simply because they grew up together and "like" each other. That is anthropomorphic. This is specifically a mating behavior which is instinctual to reptiles at this time of year. Outdoor sun brings this out in them in the spring time.

There are many different ways to prepare habitats to allow the female a comfortable place to lay her eggs. I don't know how big your kiddie pool is, but a kiddie pool is probably not going to be big enough for extended stay by a mature female slider looking for a place to deposit eggs. Once sliders and other aquatic turtles reach maturity and there is going to be breeding, I recommend outdoor pond habitats; like a concrete basin several feet in diameter and a couple of feet deep at the least, with logs and other functional decor. She needs to have constant access to not only her natural aquatic environment, but to plenty of dry basking and nesting areas. She needs to have options, because she may not necessarily like one area for various reasons...and if she doesn't, she may hold her eggs until it harms her or the embryos.

I would recommend offering a couple of areas of sand topped with different substrates, such as bark mulch, organic humus/potting soil, or moss to a few inches. She is going to be looking for some humidity for the eggs, but not so much that they mold. Once laid, if you know where she laid them, you can remove them to an incubator, while maintaining proper right side up orientation; or, you can leave them be to incubate naturally outside if the climate is proper.     

With some websearching you can find many ideas and pictures of outdoor aquatic turtle habitats, as well as how to care for and incubate the eggs once laid.

http://anapsid.org/mainchelonians/html
http://austinsturtlepage.com