# Assuming a variable is imaginary

I am confused how to assume a variable is pure imaginary. As a test example, I used the code

Assuming[{ x \[Element] I Reals}, Simplify[x + Conjugate[x]]]


In the above, "I" means the imaginary unit. I find that it does not return me 0, but just

x + Conjugate[x]


How shall I let $$x$$ to be pure imaginary? Many thanks!

This needs FullSimplify.
FullSimplify[x + Conjugate[x], Re[x] == 0]

0