What to say to an ex to make him stop contacting me?

[Rebecca]

My (ex) boyfriend and I broke up over a year ago. He handled it very poorly and immaturely. I'm dating someone new, but he has continued to text me mean things, and finally blocked me and deleted my number.

Yesterday, he messaged me on Facebook, along the lines of "Tell me our relationship wasn't a joke, and tell me I meant something to you."

I want to respond and ask him not to contact me again, but I'm not sure how to phrase it.
Any advice?

[Sal*UK]

Nothing
Not a word
Not a sound
Do not even acknowledge that he exists

[Caelestis]

You don't say anything. Block him and change your number.

[Tom Hall]

ignore him and block him the more you respond the more he will contact you send one message "dont contact me again" then block him from anything he can contact you on