we have just been given a young snake neck turtle, i would think he is no more than 6 months? from the top to the bottom of his shell its about 8cm(ish) and from side to side is about 5-6cm. we have a young red eared which we were also given and was that size when we got him (4 months or so ago) and hes nearly trippled in size. we put them in together and they are fine , is this ok?