Need query that will return firstnames with x characters

[busboy]

I have spammers who post on my website. They like to use things like Home-loan-refinancing as their first name when registering. So I need a query that will return all rows where the firstname field contains 20+ characters or something like that. This will help me to quickly root these bad guys out and delete them.

Thanks!

[longneck]

delete from sometable
 where char_length(somecolumn) >= 20