My red-eared sliders

Question
I have 2 lovely red-eared sliders.  I take wonderful care of them.  I clean the tank regularly, change the water as I'm supposed to and feed them what is required.
They are both the same age( supposedly brother and sister), around 4 years old.
My problem is that the male turtle is constantly biting and harassing the female.  He bites her neck, her legs and her tail.  Recently I have discovered black patches on her tail and legs.  What is causing this?  Should I take her to a Vet, or is there something you can suggest that will help her.?
Thank you for your time.

Dianne

Answer
I thought I already answered this, but in case it did not get sent, it is probably either a courtship display, or a dominance display. If the tank is small for them, it is more likely the dominance bit.

If the marks are small and do not appear inflammed or growing, and the female does not appear too stressed by this, I would just make sure that the basi cares are solid and the hygiene is good. If things get worse, I'd try a bigger cage and watch again.

If the marks become actual wounds, go to a dry tank process and treat the injuries. If it gets this bad, you may have to seperate them, at least for a while.