I have about 20-30 existing domains, all getting a small amount of traffic each. If I were to forward all 30 domains to 1 Domain, would this affect your ranking in a negative way? Is this an overall good or bad idea?
I don't think it will affect the ranking at all... if you get few visitors on each domain, that will be no problem
To be on the safe side you shouldn't do them all at once, 20-30 domains all at once would be a little suspicious.
You mean a 301 or a meta-refresh? A 301 may be risky if you do 20-30 at once. Agree with guy above, start slow.