Thread:Project:Support desk/Bots regsiter at my wiki website! How to stop them?

I have installed wiki and some bots started to register. So I use captcha extension, but it doesn't help Here you can look at users that were registered > http://www.allwikilyrics.com/index.php/Special:ListUsers Users like CasandraRuggiero982, MccutchenCimino102, TootsiePonder591 are bots I guess. Why can they go trhough the registration! Could you help what can you advice?