Completly new Forum -> wich anti-spam-mod?

I set up a PunBB (it's my first, I like the philosophy behind it)

Guest shall have the right to post new topics and responses
and there should be no verification email, if someone wants to register.

So, I think, I will need an anti-spam-mod, am I right?

I searched punres.org and found:

Aksimet
Captchabox
Spam protection

Which one should I use?
Or maybe two, or maybe all three?
Or maybe something completly different?