registration spam

Hi,
Over the holidays, updated from 2.9.x to 3.0.4 and suddenly I am getting about 5-10 ‘fake’ registrations to my site every day. Most of the names are just nonsense characters and a lot of the addresses are .ru domains. I have installed Bad Behavior, Askimet, and Stop Spammer Registrations Plugin, but after a week I still get multiple registrations a day.

I have read through the forums here, and see solutions for comment spam, which isn’t my problem exactly — I don’t want them to register at all. They are not actually making comments, but it is annoying to have to manually delete 10 or so new users a day.

You don’t have to register to make a comment on my site, but we are open to allowing ‘real’ people to register so that they can make new posts and be ‘trusted’ to let all their comments through. Is there a way I can make it harder for bots or spammers to register?

Site is https://www.cafetableaux.com/

Thanks in advance.