Changing piano-black theme

Oh sorry, an additional question. What anti-spam plugin could I use for this theme? I tried SI CAPTCHA Anti-Spam, but for some reason the captcha box won’t display for my users, all it does is don’t let them post.

Thank you, I fixed the image already.

How about a captcha system for piano-black? I enable the SI CAPTCHA Anti-Spam plugin, but all it does is tell people they didn’t fill the captcha when posting, while the captcha doesn’t appear on the posting screen.

I really need it since I’ve got over 300 spam comments. Preferably one that doesn’t look too ugly.

Edit: I’ve tried Really Simple Captcha Comments, and I have the same issue. There is no captcha box like there should be:

http://www.xrdnet.com/sgz/?p=712

What do I need to edit in order for the captcha to appear, in case of this plugin? Note: Yes I’ve installed Really Simple Captcha, too.