Yep you're right about having to breed to hets. Originally I was going to breed them, I had two full grown males and they got along fine but I sold one of them, and kept the one in with my diamondback terrapins, they were full grown when the terrapins were hatchlings, so the turtles grew up with them always in the tank, so they never saw them as food, just tank buddies. Here is a pic I took 2 years ago of the big male, he was every bit of 6-7 inches.

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Jeff Benfer
gartersnakemorph.com