At what age can male and females be put together in a tank?

[Eridu Serpent]

Well I have tried a few times introducing Goober to Pickle and I did it each time they were fully fed...Goober goes for her.
I thought it may be because it is his tank so I tried in hers and then on the floor on a towel.
He just does not seem to like her.
I measured her and she is 3.5 inches and he is nearly 6.5...I even sat her on top of him and his mouth seems big enough to eat her.
I appreciate all the info and the being told that they are not as cannibalistic etc etc but I am way too scared to risk it.
There is no way I could watch them 24/7 ...I´d be a nervous wreck!

So I have excepted Pablos offer to exchange her for a male, at least at some point it will be big enough to put in the same tank.

THANK you though for all your help