Create an effective anti-spam signup solution

I have a website running on Wordpress that has, until fairly recently, used the Captcha plugin by SimplyWordpress. As you're no doubt aware, that plugin has been discontinued, due to security reasons. I replaced this captcha with a math-based one, but it isn't stopping sign-ups. I am currently looking for an effective replacement that keeps the daily nonsensical registrations from happening. I'm open to solutions beyond a captcha, too. If you have a better method that does NOT include Google's captcha, I may be interested. I need this to be done smoothly and want it to look good/integrate well with my current custom login page. Please only apply for this job if you have experience doing this sort of work. I don't want hacks, I want professional ideas that I haven't considered yet.