red-ear slider biting

Question
For the past couple of years, whenever I put my two red-eared sliders together, the male bites the female.  So far, he has not drawn blood, but it is very scary to find them at the bottom of the pool, face to face, heads drawn in, with him hanging onto her neck!  I was afraid she would not be able to breathe.  It doesn't matter whether they are in the 50 gal tank or the large Coleco kiddie wading pool, so I don't think territory disputes have anything to do with this.  (His shell 5 in. long, hers is 6. She was purchased as an adult in 1980; he was bought as an adult in
1990.) Frankly, I think he is attracted to her.  Would it be safe to leave them together & let nature take its course?  Or should I
continue to keep them apart?  My original pair of red-eared
turtles (also male & female) generally left each other alone.  Mating behavior was clearly seasonal, and the only
parts nibbled on were toes, and that was rare. With these
two, this behavior is year-round.  Ironically, I bought the
male to keep her company when the original male died at the age of 29.  Now I'm afraid to leave them alone together.
Thank you very much for any help you can give me!

Answer
Some guys are just like that, unfortunately. It may have started because of crowding or something (2 near-adults in a 50 is very tight, and a baby pool not very filled is usually not a lot better). If they do it even in a bigger pool, he may just be a bully.

Try http://www.turtleforum.com for more ideas. Good luck!